3,6-disubstituted xanthylium salts and use thereof in treatment of tauopathies

ABSTRACT

This invention pertains generally to processes, uses, methods and materials utilizing particular xanthylium compounds, including compounds of formula (I) and (II), as further defined herein. These compounds are useful as drugs, for example, in the treatment of tauopathies, such as Alzheimer&#39;s disease.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is the U.S. National Phase of PCT/GB2009/002865, filedDec. 10, 2009, which was published in English on Jun. 17, 2010, as WO2010/067078, and which claims priority from U.S. Provisional ApplicationNo. 61/121,288, filed Dec. 10, 2008, all of which are incorporatedherein by reference in entirety.

TECHNICAL FIELD

This invention pertains generally to processes, uses, methods andmaterials utilising particular xanthylium compounds. These compounds areuseful as drugs, for example, in the treatment of tauopathies, such asAlzheimer's disease.

BACKGROUND

A number of patents and publications are cited herein in order to morefully describe and disclose the invention and the state of the art towhich the invention pertains. Each of these references is incorporatedherein by reference in its entirety into the present disclosure, to thesame extent as if each individual reference was specifically andindividually indicated to be incorporated by reference.

Throughout this specification, including the claims which follow, unlessthe context requires otherwise, the word “comprise,” and variations suchas “comprises” and “comprising,” will be understood to imply theinclusion of a stated integer or step or group of integers or steps butnot the exclusion of any other integer or step or group of integers orsteps.

It must be noted that, as used in the specification and the appendedclaims, the singular forms “a,” “an,” and “the” include plural referentsunless the context clearly dictates otherwise. Thus, for example,reference to “a pharmaceutical carrier” includes mixtures of two or moresuch carriers, and the like.

Ranges are often expressed herein as from “about” one particular value,and/or to “about” another particular value. When such a range isexpressed, another embodiment includes from the one particular valueand/or to the other particular value. Similarly, when values areexpressed as approximations, by the use of the antecedent “about,” itwill be understood that the particular value forms another embodiment.

Conditions of dementia such as Alzheimer's disease (AD) are frequentlycharacterised by a progressive accumulation of intracellular and/orextracellular deposits of proteinaceous structures such as β-amyloidplaques and neurofibrillary tangles (NFTs) in the brains of affectedpatients. The appearance of these lesions largely correlates withpathological neurofibrillary degeneration and brain atrophy, as well aswith cognitive impairment (see, e.g., Mukaetova-Ladinska, E. B., et al.,2000, Am. J. Pathol., Vol. 157, No. 2, pp. 623-636).

In AD, both neuritic plaques and NFTs contain paired helical filaments(PHFs), of which a major constituent is the microtubule-associatedprotein tau (see, e.g., Wischik et al., 1988, PNAS USA, Vol. 85, pp.4506-4510). Plaques also contain extracellular β-amyloid fibrils derivedfrom the abnormal processing of amyloid precursor protein (APP) (see,e.g., Kang et al., 1987, Nature, Vol. 325, p. 733). An article byWischik et al. (in ‘Neurobiology of Alzheimer's Disease’, 2nd Edition,2000, Eds. Dawbarn, D. and Allen, S. J., The Molecular and CellularNeurobiology Series, Bios Scientific Publishers, Oxford) discusses indetail the putative role of tau protein in the pathogenesis ofneurodegenerative dementias. Loss of the normal form of tau,accumulation of pathological PHFs, and loss of synapses in themid-frontal cortex all correlate with associated cognitive impairment.Furthermore, loss of synapses and loss of pyramidal cells both correlatewith morphometric measures of tau-reactive neurofibrillary pathology,which parallels, at a molecular level, an almost total redistribution ofthe tau protein pool from a soluble to a polymerised form (i.e., PHFs)in Alzheimer's disease.

Tau exists in alternatively-spliced isoforms, which contain three orfour copies of a repeat sequence corresponding to themicrotubule-binding domain (see, e.g., Goedert, M., et al., 1989, EMBOJ., Vol. 8, pp. 393-399; Goedert, M., et al., 1989, Neuron, Vol. 3, pp.519-526). Tau in PHFs is proteolytically processed to a core domain(see, e.g., Wischik, C. M., et al., 1988, PNAS USA, Vol. 85, pp.4884-4888; Wischik et al., 1988, PNAS USA, Vol. 85, pp. 4506-4510;Novak, M., et al., 1993, EMBO J., Vol. 12, pp. 365-370) which iscomposed of a phase-shifted version of the repeat domain; only threerepeats are involved in the stable tau-tau interaction (see, e.g.,Jakes, R., et al., 1991, EMBO J., Vol. 10, pp. 2725-2729). Once formed,PHF-like tau aggregates act as seeds for the further capture and providea template for proteolytic processing of full-length tau protein (see,e.g., Wischik et al., 1996, PNAS USA, Vol. 93, pp. 11213-11218).

The phase shift which is observed in the repeat domain of tauincorporated into PHFs suggests that the repeat domain undergoes aninduced conformational change during incorporation into the filament.During the onset of AD, it is envisaged that this conformational changecould be initiated by the binding of tau to a pathological substrate,such as damaged or mutated membrane proteins (see, e.g., Wischik, C. M.,et al., 1997, in “Microtubule-associated proteins: modifications indisease”, Eds. Avila, J., Brandt, R. and Kosik, K. S. (Harwood AcademicPublishers, Amsterdam) pp. 185-241).

In the course of their formation and accumulation, PHFs first assembleto form amorphous aggregates within the cytoplasm, probably from earlytau oligomers which become truncated prior to, or in the course of, PHFassembly (see, e.g., Mena, R., et al., 1995, Acta Neuropathol., Vol. 89,pp. 50-56; Mena, R., et al., 1996, Acta Neuropathol., Vol. 91, pp.633-641). These filaments then go on to form classical intracellularNFTs. In this state, the PHFs consist of a core of truncated tau and afuzzy outer coat containing full-length tau (see, e.g., Wischik et al.,1996, PNAS USA, Vol. 93, pp. 11213-11218). The assembly process isexponential, consuming the cellular pool of normal functional tau andinducing new tau synthesis to make up the deficit (see, e.g., Lai, R. Y.K., et al., 1995, Neurobiology of Ageing, Vol. 16, No. 3, pp. 433-445).Eventually, functional impairment of the neurone progresses to the pointof cell death, leaving behind an extracellular NFT. Cell death is highlycorrelated with the number of extracellular NFTs (see, e.g., Wischik etal., in ‘Neurobiology of Alzheimer's Disease’, 2nd Edition, 2001, Eds.Dawbarn, D. and Allen, S. J., The Molecular and Cellular NeurobiologySeries, Bios Scientific Publishers, Oxford). As tangles are extrudedinto the extracellular space, there is progressive loss of the fuzzyouter coat of the neurone with corresponding loss of N-terminal tauimmunoreactivity, but preservation of tau immunoreactivity associatedwith the PHF core (see, e.g., Bondareff, W. et al., 1994, J. Neuropath.Exper. Neurol., Vol. 53, No. 2, pp. 158-164).

Xanthylium compounds (also known as pyronine compounds) have previouslybeen shown to act as fluorescent dyes. Xanthylium compounds previouslydisclosed include:

Compound Structure and Name Citation A

See e.g.: U.S. Pat. No. 3,932,415 C

See e.g.: Haley et al. X

See e.g.: Prostota et al. E

See e.g.: J. Biehringer Journal Fur Praktische Chemie G

See e.g.: JP 2000 344684 Chamberlin et al. LZ

See e.g.: Nealey et al. LP

See e.g.: Müller et al. MC

See e.g.: Gloster et al. MP

See e.g.: Müller et al. O

See e.g.: Müller et al. Y

See e.g.: Albert Z

See e.g.: DE 65282 AA

See e.g.: JP 2000/344684 AL

See e.g.: Laursen, et al

JP 2000/344684 describes the use of xanthylium compounds, such ascompound G and AA, as probes for diseases which accumulate β-amyloidprotein.

WO 96/30766 describes the use of a xanthylium compound, DMAXC, ascapable of inhibiting tau-tau protein interactions:

Compound Structure and Name DMAXC

Diaminophenothiazines have previously been shown to inhibit tau proteinaggregation and to disrupt the structure of PHFs, and reverse theproteolytic stability of the PHF core (see, e.g., WO 96/30766, FHoffman-La Roche). Such compounds were disclosed for use in thetreatment or prophylaxis of various diseases, including Alzheimer'sdisease. These included, amongst others:

Compound Structure and Name MTC

DMMTC

It will be understood that the term ‘xanthylium compounds’, as usedherein, refers generally to compounds having a xanthylium core structureand compounds having related core structures including, but not limitedto thioxanthylium, phenazinium, oxazinium, and thioninium.

Notwithstanding the above disclosures, it will be appreciated that theprovision of one or more xanthylium compounds, not previouslyspecifically identified as being effective tau protein aggregationinhibitors, would provide a contribution to the art.

DESCRIPTION OF THE INVENTION

The present inventors have now identified certain xanthylium compoundsas being effective tau protein aggregation inhibitors and in preferredforms having certain other desirable properties, for example bycomparison with the compounds of the prior art discussed above.

As discussed above, tau proteins are characterised as being one among alarger number of protein families which co-purify with microtubulesduring repeated cycles of assembly and disassembly (Shelanski et al.Proc. Natl. Acad. Sci. USA 1973, 70, 765-768), and are known asmicrotubule-associated-proteins (MAPs). Members of the tau family sharethe common features of having a characteristic N-terminal segment,sequences of approximately 50 amino acids inserted in the N-terminalsegment, which are developmentally regulated in the brain, acharacteristic tandem repeat region consisting of 3 or 4 tandem repeatsof 31-32 amino acids, and a C-terminal tail.

One or more of the xanthylium compounds are known in the art—for examplecompound A(2,3,6,7,12,13,16,17-Octahydro-1H,5H,11H,15H-diquinolizino[1,9-bc:1′,9′-hi]xanthyliumchloride) is described in U.S. Pat. No. 3,932,415. However it isbelieved that none of these have previously been disclosed in the priorart as tau protein aggregation inhibitors.

The invention therefore relates to methods, uses, compositions and othermaterials employing these compounds as tau protein aggregationinhibitors and as therapeutics or prophylactics of diseases associatedwith tau protein aggregation (“tauopathies”). The invention furtherprovides processes for making these compounds.

These and other aspects of the invention are discussed in more detailhereinafter.

Compounds

In one aspect the present invention provides compounds of formula (I),and particularly their use in medicine:

-   -   wherein:    -   X⁻ is an anion;    -   —R⁵ is independently —H, or saturated C₁₋₆alkyl, which is        unsubstituted or substituted with one or more substituents        —R^(5A), or phenyl, which is unsubstituted or substituted with        one or more substituents —R^(6A);    -   each —R^(5A) is independently selected from —F, —Cl, —Br, —I,        —OH, —OR⁶, —SH, —SR⁶, —CN, —NO₂, —NH₂, —NHR⁶, —NR⁶ ₂,        —NHC(═O)R⁶, —NR⁶C(═O)R⁶, —C(═O)OR⁶, —OC(═O)R⁶, —C(═O)NH₂,        —C(═O)NHR⁶, —C(═O)NR⁶ ₂, —C(═O)R⁶, —C(═O)OH, —S(═O)R⁶,        —S(═O)₂R⁶, and —S(═O)₂OH; and    -   each —R⁶ is independently saturated aliphatic C₁₋₄alkyl, phenyl,        or benzyl;    -   —R^(13a), —R^(13b), —R^(14a), —R^(14b), —R^(15a), —R^(15b),        —R^(16a), and —R^(16b) are each independently selected from H        and saturated aliphatic C₁₋₄ alkyl.

In one embodiment —R^(13a), —R^(13b), —R^(14a), —R^(14b), —R^(15a),—R^(15b), —R^(16a), and —R^(16b) are all H, providing a compound offormula (Ic).

-   -   wherein X and R⁵ are as defined above.

In one embodiment —R⁵ is independently —H, or saturated C₁₋₆alkyl, whichis unsubstituted or substituted with one or more substituents —R^(5A).

In one embodiment, the compound of the invention is a compound offormula (I) or (I′) with the proviso that the compound is not:

-   2,3,6,7,12,13,16,17-octahydro-1H,5H,11H,15H-diquinolizino[1,9-bc:1′,9′-hi]xanthylium    chloride (“compound A”);-   8-(trifluoromethyl)-2,3,5,6,11,12,14,15-octahydro-1H,4H,10H,13H-diquinolizino[9,9a,1-bc;9′,9a′1′-hi]xanthylium    perchlorate (“compound C”); or-   2,3,6,7,12,13,16,17-octahydro-1H,5H,11H,15H-diquinolizino[1,9-bc:1′,9′-hi]xanthylium    perchlorate (“compound X”).

In a further aspect of the present invention there are providedcompounds of formula (II) and particularly their use in medicine:

-   -   wherein:    -   X⁻ is a counter ion;    -   Y is O, and Z is N or C—R⁵; or    -   Y is S, and Z is C—R⁵;    -   —R¹ and —R², are each independently saturated C₁₋₆alkyl,    -   or R¹ and R², together with the nitrogen atom to which they are        bound, form a saturated C₃₋₇ heterocycle;    -   —R³ and —R⁴ are each independently saturated C₁₋₆alkyl, or R³        and R⁴, together with the nitrogen atom to which they are bound,        form a saturated C₃₋₇ heterocycle;    -   —R⁵ is independently —H, saturated C₁₋₆alkyl, which is        unsubstituted or substituted with one or more substituents        —R^(5A), or phenyl, which is unsubstituted or substituted with        one or more substituents —R^(5A-);    -   each —R^(5A) is independently selected from —F, —Cl, —Br, —I,        —OH, —OR⁶, —SH, —SR⁶, —CN, —NO₂, —NH₂, —NHR⁶, —NR⁶ ₂,        —NHC(═O)R⁶, —NR⁶C(═O)R⁶, —C(═O)OR⁶, —OC(═O)R⁶, —C(═O)NH₂,        —C(═O)NHR⁶, —C(═O)NR⁶ ₂, —C(═O)R⁶, —C(═O)OH, —S(═O)R⁶,        —S(═O)₂R⁶, and —S(═O)₂OH;    -   each —R⁶ is independently saturated aliphatic C₁₋₄alkyl, phenyl,        or benzyl; and    -   —R⁷ and —R⁸ are each independently selected from: —H, saturated        C₁₋₄alkyl, C₂₋₄alkenyl, and halogenated C₁₋₄alkyl; and    -   additionally, when Z is C—R⁵ and R⁵ is phenyl, —R⁷ and —R⁸ may        each independently be a bridging group, W, which is bonded to        said R⁵; and    -   W is O, NR¹⁷, S, or C(R¹⁷)₂ wherein each R¹⁷ is independently        selected from H, saturated aliphatic C₁₋₄ alkyl, and R^(5A).

In one embodiment, —R¹, —R², —R³ and —R⁴ are each independentlysaturated aliphatic C₁₋₆alkyl.

In one embodiment, —R⁷ and —R⁸ are each independently selected from: —H,saturated C₁₋₄alkyl, C₂₋₄alkenyl, and halogenated C₁₋₄alkyl.

In one embodiment, —R⁵ is independently —H, saturated C₁₋₆alkyl, whichis unsubstituted or substituted with one or more substituents —R^(5A).

In one embodiment, at least one of —R¹, —R², —R³ and —R⁴ isindependently unsubstituted saturated aliphatic C₂₋₆alkyl.

In one embodiment, the compound of the invention is a compound offormula (II) with the proviso that the compound is not:

-   3,6-bis(dimethylamino)thioxanthylium zinc trichloride (“compound    LZ”);-   3,6-bis(dimethylamino)thioxanthylium perchlorate (“compound LP”);-   3,7-bis(dimethylamino)phenazinium chloride (“compound MC”);-   3,7-Bis(dimethylamino)phenazinium perchlorate (“compound MP”); or-   3,7-bis(dimethylamino)oxazinium chloride (“compound O”).

In another embodiment, the compound of the invention is a compound offormula (II) with the proviso that the compound is not:

-   3,6-bis-diethylamino xanthylium chloride (“compound E”);-   3,6-bis-diethylamino xanthylium iron tetrachloride (“compound G”);    or-   3,6-bis-diethylamino xanthylium zinc trichloride (“compound Y”).

In another embodiment, the compound of the invention is a compound offormula (II) with the proviso that the compound is not9-(2-carboxyethyl)-3,6-Bis-dimethylamino xanthylium chloride (“compoundAA”).

In another embodiment, the compound of the invention is a compound offormula (II) with the proviso that the compound is not3,6-bis-dimethylamino xanthylium chloride (“DMAXC”).

In a preferred embodiment of the invention there are provided compoundsof formula (IIa) and particularly their use in medicine:

-   -   wherein:    -   X⁻ is a counter ion;        -   —R⁹, and —R¹⁰ are each independently saturated C₁₋₆alkyl; or            —R⁹ and —R¹⁰, together with the nitrogen atom to which they            are bound, form a saturated C₃₋₇ heterocycle;        -   —R¹¹ and —R¹² are each independently saturated C₁₋₆alkyl, or            —R¹¹ and —R¹², together with the nitrogen atom to which they            are bound, form a saturated C₃₋₇ heterocycle; and    -   —R⁵ is defined according to the compounds of formula (II).

In one embodiment, R⁹, —R¹⁰, —R¹¹ and —R¹² are each independentlysaturated C₂₋₆alkyl.

In one embodiment, the compound of the invention is a compound offormula (IIa) with the proviso that the compound is not:

-   3,6-bis-diethylamino xanthylium chloride (“compound E”);-   3,6-bis-diethylamino xanthylium iron tetrachloride (“compound G”);-   3,6-bis-diethylamino xanthylium zinc trichloride (“compound Y”);

In one embodiment, the compound of the invention is a compound offormula (IIa) with the proviso that the compound is not3,6-bis-dimethylamino xanthylium chloride (DMAXC).

In a preferred embodiment of the invention there are provided compoundsof formula (IIb) and particularly their use in medicine:

-   -   wherein:    -   X⁻ is a counter ion;    -   Y is O or NH, and Z is N; or    -   Y is S, and Z is C—R⁵;    -   —R¹, —R², —R³, —R⁴, —R⁵, —R⁷ and —R⁸ are defined according to        the compound of formula (II).

In one embodiment, the compound of the invention is a compound offormula (IIb) with the proviso that the compound is not:

-   3,6-bis(dimethylamino)thioxanthylium zinc trichloride (“compound    L”);-   3,7-bis(dimethylamino)phenazinium chloride (“compound M”); or-   3,7-bis(dimethylamino)oxazinium chloride (“compound O”).

In an alternative embodiment of the invention, there are providedcompounds of formula (IIc) and particularly their use in medicine:

-   -   wherein:    -   X⁻ is a counter ion;    -   Y is O or S;        -   —R⁹ and —R¹⁰ are each independently saturated C₁₋₆alkyl; -            or R⁹ and R¹⁰, together with the nitrogen atom to which they            are bound, form a saturated C₃₋₇ heterocycle;        -   —R¹¹ and —R¹² are each independently saturated C₁₋₆alkyl, or            R¹¹ and R¹², together with the nitrogen atom to which they            are bound, form a saturated C₃₋₇ heterocycle; and    -   —R⁵ is defined according to the compounds of formula (II).

In one embodiment, R⁹, —R¹⁰, —R¹¹ and —R¹² are each independentlysaturated C₂₋₆alkyl.

In one embodiment, the compound of the invention is a compound offormula (IIc) with the proviso that the compound is not:

-   3,6-bis-diethylamino xanthylium chloride (“compound E”);-   3,6-bis-diethylamine xanthylium iron tetrachloride (“compound G”);    or-   3,6-bis-diethylamino xanthylium zinc trichloride (“compound Y”)

In one embodiment, the compound of the invention is a compound offormula (IIc) with the proviso that the compound is not3,6-bis-dimethylamino xanthylium chloride (DMAXC).

In an alternative embodiment, there are provided compounds wherein Z isC—R⁵, R⁵ is phenyl, and —R⁷ and —R⁸ are each independently a bridginggroup, W, which is bonded to said R⁵, and their use in medicine.

These compounds can also be described as compounds of formula (VI):

-   -   wherein X⁻, Y, W, —R¹, —R², —R³, —R⁴ and —R^(5A) are as defined        according to the compounds of formula (II).

In one embodiment, at least one of —R¹, —R², —R³ and —R⁴ isindependently unsubstituted saturated aliphatic C₂₋₆alkyl.

In one embodiment, the compound of the invention is a compound offormula (VI) with the proviso that the compound is not2,6,10-tris-diethylamino-4,8,12-trioxatrianguleum hexafluorophosphate(‘compound AL’).

In a preferred embodiment of the invention, there are provided compoundsof formula (VIa) and particularly their use in medicine:

-   -   wherein X⁻, —R¹, —R², —R³, —R⁴, —R⁵ and —R^(5A) are as defined        according to the compounds of formula (VI).

In one embodiment, the compound of the invention is a compound offormula (VIa) with the proviso that the compound is not2,6,10-tris-diethylamino-4,8,12-trioxatrianguleum hexafluorophosphate(‘compound AL’).

In a further aspect of the present invention there are providedcompounds of formula (III), and particularly their use in medicine:

-   -   wherein:    -   X⁻ is a counter ion;    -   Y is O or S;        -   —R⁹ and —R¹⁰ are each independently saturated C₁₋₆alkyl;    -   or R⁹ and R¹⁰, together with the nitrogen atom to which they are        bound, form a saturated C₃₋₇ heterocycle;        -   —R¹¹ and —R¹² are each independently saturated C₁₋₆alkyl,    -   or R¹¹ and R¹², together with the nitrogen atom to which they        are bound, form a saturated C₃₋₇ heterocycle; and    -   —R⁵ is defined according to the compounds of formula (II).

In one embodiment, R⁹, —R¹⁰, —R¹¹ and —R¹² are each independentlysaturated C₂₋₆alkyl.

In one embodiment, the compound of the invention is a compound offormula (III) with the proviso that the compound is not3,6-bis-diethylamino xanthene dihydrochloride (“compound H”).

The compounds (I), (Ic), (II), (IIa), (IIb), (IIc), (III), (VI), and(VIa) are described herein as “xanthylium compounds” or “compounds ofthe invention” or (unless context demands otherwise) “active compounds”.

The preferred counter ions and substituents for the compounds (I), (Ic),(II), (IIa), (IIb), (IIc), (III), (VI) and (Via) are set out below. Theyare combinable in any combination, where appropriate. Each and everycompatible combination of the embodiments described above, and below, isexplicitly disclosed herein, as if each and every combination wasindividually and explicitly recited.

Preferences for X⁻

X⁻ is a counter ion. X⁻ is one or more anionic counter ions to achieveelectrical neutrality.

In one embodiment, X⁻ is one anionic counter ion.

In one embodiment, each X⁻ is a pharmaceutically acceptable anion.

In one embodiment, each X⁻ may be selected from the group consisting of:NO₃ ⁻, ClO₄ ⁻, F⁻, Cl⁻, Br⁻, I⁻, ZnCl₃ ⁻, FeCl₄ ⁻, and PF₆ ⁻.

In one embodiment, each X⁻ may be selected from the group consisting of:NO₃, ClO₄ ⁻, Cl⁻, Br⁻, I⁻, FeCl₄ ⁻, and PF₆ ⁻.

In one embodiment, each X⁻ may be selected from NO₃ ⁻, Cl⁻, and ClO₄ ⁻.

In one embodiment, each X⁻ may be selected from NO₃ ⁻, Cl⁻, Br andFeCl₄.

In one embodiment, each X⁻ may be selected from I⁻, Br, NO₃ ⁻ and Cl⁻.

In one embodiment, each X⁻ may be selected from I⁻, NO₃ ⁻ and Cl⁻.

X⁻ may be ZnCl₃ ⁻.

X⁻ may be NO₃ ⁻.

X⁻ may be Cl⁻.

X⁻ may be ClO₄ ⁻.

X⁻ may be Br⁻.

X⁻ may be I⁻.

X⁻ may be FeCl₄ ⁻.

X⁻ may be PF₆ ⁻.

In one embodiment, X⁻ is a mixed anionic counter ion. In one embodiment,the compound is in the form of a mixed salt, for example, a HNO₃ mixedsalt. In one embodiment the compound is in the form of a NO₃ ⁻ and HNO₃mixed salt.

Preferences for —R^(13a), —R^(13b), —R^(14a), —R^(14b), —R^(15a),—R^(16a), and —R^(16b)

—R^(13a), —R^(13b), —R^(14a), —R^(14b), —R^(15a), —R^(15b), —R^(16a),and —R^(16b) are each independently selected from H and saturatedaliphatic C₁₋₄ alkyl.

In one embodiment, —R^(13a), —R^(13b), —R^(14a), —R^(14b), —R^(15a),—R^(15b), —R^(16a), and —R^(16b) are each independently H.

In one embodiment, —R^(13a), —R^(14a), —R^(14b), —R^(15a), —R^(15b),—R^(16a), and —R^(16b) are all H.

In one embodiment, —R^(13a), —R^(13b), —R^(14a), —R^(15a), —R^(15b),—R^(16a), and —R^(16b) are each independently saturated aliphatic C₁₋₄alkyl.

In one embodiment, —R^(13a), —R^(14a), —R^(14b), —R^(15a), —R^(15b),—R^(16a), and —R^(16b) are each independently selected from methyl,ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, and t-butyl.

In one embodiment, —R^(13a), —R^(13b), —R^(14a), —R^(14b), —R^(15a),—R^(15b), —R^(16a), and —R^(16b) are each independently methyl or ethyl.

In one embodiment, —R^(13a), —R^(13b), —R^(14a), —R^(14b), —R^(15a),—R^(15b), —R^(16a), and R^(16b) are each independently methyl.

In one embodiment, —R^(13a), —R^(13b), —R^(14a), —R^(14b), —R^(15a),—R^(15b), —R^(16a), and —R^(16b) are all methyl.

Preferences for Y, Z, and W

For the compounds of formula (II), Y is independently O, NH or S.

In one embodiment, Y is O.

In one embodiment, Y is NH.

In one embodiment, Y is S.

In one embodiment, Y is O or NH, and Z is N.

In one embodiment, Y is O or S, and Z is C—R⁵.

In one embodiment, Y is O, and Z is N or C—R⁵.

In one embodiment, Y is O, and Z is N.

In one embodiment, Y is O, and Z is C—R⁵.

In one embodiment, Y is NH, and Z is N.

In one embodiment, Y is S, and Z is C—R⁵.

For the compounds of formula (IIb), Y is independently O, NH or S.

In one embodiment, Y is O, and Z is N.

In one embodiment, Y is NH, and Z is N.

In one embodiment, Y is S, and Z is C—R⁵.

For the compounds of formula (IIc), Y is independently O or S.

In one embodiment, Y is O.

In one embodiment, Y is S.

For the compounds of formula (III), Y is independently O or S.

In one embodiment, Y is O.

In one embodiment, Y is S.

For the compounds of formula (IV), Y is independently O, NH or S.

In one embodiment, Y is O.

In one embodiment, Y is NH.

In one embodiment, Y is S.

Each W is independently O, NR¹⁷, CR¹⁷ ₂, or S.

In one embodiment, each W is independently O, NR¹⁷ or S.

In one embodiment, each W is independently O, NH or S.

In one embodiment, each W is independently O or S.

In one embodiment, each W is independently O.

In one embodiment, each W is independently CR¹⁷ ₂.

In one embodiment, each W is independently CH₂.

Preferences for —R¹⁷

Each R¹⁷ is independently H, saturated aliphatic C₁₋₄ alkyl, or is asdefined for R^(5A).

In one embodiment, each R¹⁷ is H.

In one embodiment, each R¹⁷ is independently H or saturated aliphaticC₁₋₄ alkyl.

In one embodiment, each R¹⁷ is independently saturated aliphatic C₁₋₄alkyl.

In one embodiment, each R¹⁷ is independently selected from methyl,ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, and t-butyl.

In one embodiment, each R¹⁷ is independently selected from H or methyl.

In one embodiment W is NR¹⁷ and R¹⁷ is H or saturated aliphatic C₁₋₄alkyl.

In one embodiment W is NR¹⁷ and R¹⁷ is H.

In one embodiment W is NR¹⁷ and R¹⁷ is saturated aliphatic C₁₋₄ alkyl.

In one embodiment W is C(R¹⁷)₂ and each R¹⁷ is H or saturated aliphaticC₁₋₄ alkyl.

In one embodiment W is C(R¹⁷)₂ and each R¹⁷ is H.

In one embodiment W is C(R¹⁷)₂ wherein one R¹⁷ is H and the other issaturated aliphatic C₁₋₄ alkyl.

In one embodiment W is C(R¹⁷)₂ and each R¹⁷ is saturated aliphatic C₁₋₄alkyl.

Preferences for —R¹, —R², —R³ and —R⁴

In one embodiment, —R¹ and —R², are each independently saturatedC₁₋₆alkyl, or R¹ and R², together with the nitrogen atom to which theyare bound, form a saturated C₃₋₇ heterocycle; and —R³ and —R⁴ are eachindependently saturated C₁₋₆alkyl, or R³ and R⁴, together with thenitrogen atom to which they are bound, form a saturated C₃₋₇heterocycle.

In one embodiment, —R¹, —R², —R³ and —R⁴ are each independentlysaturated aliphatic C₁₋₆alkyl.

In one embodiment, at least one of —R¹, —R², —R³ and —R⁴ isindependently saturated aliphatic C₂₋₆alkyl.

In one embodiment, —R¹, —R², —R³ and —R⁴ are each independentlysaturated aliphatic C₂₋₆alkyl.

In one embodiment, —R¹, —R², —R³ and —R⁴ are each independentlysaturated C₃₋₆cycloalkyl.

In one embodiment, at least one of —R¹, —R², —R³ and —R⁴ isindependently saturated C₃₋₆cycloalkyl.

In one embodiment, —R², —R³ and —R⁴ are defined according to —R⁹, —R¹⁰,R¹¹ and —R¹² respectively.

In one embodiment, —R¹ and —R² are the same.

In one embodiment, —R¹ and —R² are each -Me.

In one embodiment, —R¹ and —R² are each -Et.

In one embodiment, —R¹ and —R³ are the same.

In one embodiment, —R³ and —R³ are the same.

In one embodiment, —R³ and —R⁴ are each -Me.

In one embodiment, —R³ and —R⁴ are each -Et.

In one embodiment, —R² and —R⁴ are the same.

In one embodiment, one of —R¹ and —R² is -Me.

In one embodiment, one of —R¹ and —R² is -Et.

In one embodiment, one of —R³ and —R³ is -Me.

In one embodiment, one of —R³ and —R³ is -Et.

In one embodiment, —R¹, —R², —R³ and —R⁴ are each -Me.

In one embodiment, —R¹, —R², —R³ and —R⁴ are each -Et.

In one embodiment, —R¹ and —R², together with the nitrogen atom to whichthey are bound, form a saturated C₃₋₇ heterocycle; and —R³ and —R⁴,together with the nitrogen atom to which they are bound, independentlyform a saturated C₃₋₇ heterocycle.

In one embodiment the saturated C₃₋₇ heterocycle formed by R¹ and R² andthe saturated C₃₋₇ heterocycle formed by R³ and R⁴ are independentlyselected from: aziridine, azetidine, pyrrolidine, imidazolidine,pyrazolidine, oxazolidine, isoxazolidine, piperidine, piperazine,morpholine, azepine, oxazepine, and diazepine.

In one embodiment the saturated C₃₋₇ heterocycle formed by R¹ and R² andthe saturated C₃₋₇ heterocycle formed by R³ and R⁴ are independentlyselected from: morpholine, piperidine, and pyrrolidine.

In one embodiment the saturated C₃₋₇ heterocycle is morpholine.

In one embodiment the saturated C₃₋₇ heterocycle is piperidine.

In one embodiment the saturated C₃₋₇ heterocycle is pyrrolidine.

In one embodiment the saturated C₃₋₇ heterocycle formed by R¹ and R² andthe saturated C₃₋₇ heterocycle formed by R³ and R⁴ are the same.

Preferences for —R⁵ and —R^(5A)

In one embodiment, —R⁵ is independently —H, saturated C₁₋₆alkyl, whichis unsubstituted or substituted with one or more substituents —R^(5A),or phenyl, which is unsubstituted or substituted with one or moresubstituents —R^(5A). —R^(5A) is independently selected from —F, —Cl,—Br, —I, —OH, —SH, —SR⁶, —CN, —NO₂, —NH₂, —NHR⁶, —NR⁶ ₂, —NHC(═O)R⁶,—NR⁶C(═O)R⁶, —C(═O)OR⁶, —OC(═O)R⁶, —C(═O)NH₂, —C(═O)NHR⁶, —C(═O)NR⁶ ₂,—C(═O)R⁶, —C(═O)OH, —S(═O)R⁶, —S(═O)₂R⁶, and —S(═O)₂OH.

In one embodiment, —R⁵ is —H.

In one embodiment, —R⁵ is saturated aliphatic C₁₋₆alkyl, which isunsubstituted or substituted with one or more substituents —R^(5A).

In one embodiment, —R⁵ is saturated C₃₋₆cycloalkyl or saturatedaliphatic C₁₋₄alkyl, both of which are unsubstituted or substituted withone or more substituents —R^(5A).

In one embodiment, —R⁵ is saturated C₃₋₆cycloalkyl, which isunsubstituted or substituted with one or more substituents —R^(5A).

In one embodiment, —R⁵ is unsubstituted saturated aliphatic C₁₋₄alkyl.

In one embodiment, —R⁵ is saturated aliphatic C₁₋₄alkyl, which isunsubstituted or substituted with one or more substituents —R^(5A).

In one embodiment, —R⁵ is C₁₋₄alkyl substituted with one or moresubstituents —R^(5A).

In one embodiment, —R⁵ is saturated aliphatic C₁₋₄alkyl substituted withone or more substituents

In one embodiment, —R⁵ is -Me or -Et, which is unsubstituted orsubstituted with one or more substituents —R^(5A).

In one embodiment, —R⁵ is —CF₃ or -Et.

In one embodiment, —R⁵ is —CF₃.

In one embodiment, —R⁵ is -Et.

In one embodiment, —R⁵ is independently phenyl, which is unsubstitutedor substituted with one or more substituents —R^(5A).

In one embodiment, —R⁵ is independently phenyl, which is substitutedwith one or more substituents —R^(5A).

When R⁵ is phenyl, it may be substituted with one or more substituents—R^(5A) in a position ortho, meta or para to the tricyclic core.

In one embodiment, a substituent —R^(5A) is in the ortho position.

In one embodiment, a substituent —R^(5A) is in the meta position.

In one embodiment, a substituent —R^(5A) is in the para position.

In one embodiment, each —R^(5A) is independently selected from —F, —Cl,—Br, —I, —OH, —OR⁶, —SR⁶, —NO₂, —NH₂, —NHR⁶, —NR⁶ ₂, —NHC(═O)R⁶,—NR⁶C(═O)R⁶, —C(═O)OR⁶, —OC(═O)R⁶, —C(═O)NH₂, —C(═O)NHR⁶, —C(═O)NR⁶ ₂,—C(═O)R⁶, and —C(═O)OH.

In one embodiment, each —R^(5A) is independently selected from —F, —Cl,—Br, —I, —OH, —OR⁶, —SR⁶, —NO₂, —NH₂, —NHR⁶, —NR⁶ ₂, —NHC(═O)R⁶,—NR⁶C(═O)R⁶, —C(═O)OR⁶, —OC(═O)R⁶, —C(═O)NH₂, —C(═O)NHR⁶, and —C(═O)NR⁶₂, and —C(═O)R⁶.

In one embodiment, each —R^(5A) is independently selected from —F, —Cl,—Br, —I, —OH, —OR⁶, —SR⁶, —NO₂, —NH₂, —NHR⁶, and —NR⁶ ₂,

In one embodiment, each —R^(5A) is independently selected from —F, —Cl,—Br, —I, or —OH.

In one embodiment, each —R^(5A) is independently selected from —F, —Cl,—Br, or —I.

In one embodiment, each R^(5A) is independently selected from —NH₂,—NHR⁶, —NR⁶ ₂ and —NO₂.

In one embodiment, each R^(5A) is independently selected from —NR⁶ ₂ and—NO₂.

In one embodiment, —R⁵ is substituted with one substituent —R^(5A).

In one embodiment, —R⁵ is substituted with two substituents —R^(5A). Thesubstituents may be the same or different.

In one embodiment, —R⁵ is substituted with three substituents —R^(5A).The substituents may be the same or different.

Preferences for —R⁶

Each —R⁶ is independently saturated aliphatic C₁₋₄alkyl, phenyl, orbenzyl.

In one embodiment, —R⁶ is saturated aliphatic C₁₋₄alkyl.

In one embodiment, —R⁶ is phenyl.

In one embodiment, —R⁶ is benzyl.

Preferences for —R⁷ and —R⁸

—R⁷ and —R⁸ are each independently selected from: —H, saturatedC₁₋₄alkyl, C₂₋₄alkenyl, and halogenated C₁₋₄alkyl; and

additionally, when Z is C—R⁵ and R⁵ is phenyl, —R⁷ and —R⁸ may eachindependently be a bridging group, W, which is bonded to said R⁵.

In one embodiment —R⁷ and —R⁸ are each independently selected from: —H;saturated C₁₋₄alkyl; C₂₋₄alkenyl; and halogenated C₁₋₄alkyl.

In one embodiment, —R⁷ and —R⁸ are each independently —H.

In one embodiment, the C₁₋₄ alkyl groups are selected from: linearC₁₋₄alkyl groups, such as -Me, -Et, -nPr, -iPr, and -nBu; branchedC₃₋₄alkyl groups, such as -iPr, -iBu, -sBu, and -tBu; and cyclicC₃₋₄alkyl groups, such as -cPr and -cBu.

In one embodiment, the C₂₋₄alkenyl groups are selected from linearC₁₋₄alkenyl groups, such as —CH═CH₂ (vinyl) and —CH₂—CH═CH₂ (allyl).

In one embodiment, the halogenated C₁₋₄alkyl groups are selected from:—CF₃, —CH₂CF₃, and —CF₂CF₃.

in one embodiment, each of —R⁷ and —R⁸ independently —H, or saturatedaliphatic C₁₋₄alkyl.

In one embodiment, each of —R⁷ and —R⁸ is independently C₁₋₄alkyl.

In one embodiment, each of —R⁷ and —R⁸ is independently —H, -Me, -Et, or—CF₃.

In one embodiment, each of —R⁷ and —R⁸ is independently —H, -Me, or -Et.

In one embodiment, each of —R⁷ and —R⁸ is independently —H.

In one embodiment, each of —R⁷ and —R⁸ is independently -Me.

In one embodiment, each of —R⁷ and —R⁸ is independently -Et.

In one embodiment, —R⁷ and —R⁸ are the same.

In one embodiment, —R⁷ and —R⁸ are different.

In one embodiment, when Z is C—R⁵ and R⁵ is phenyl, —R⁷ and —R⁸ may eachindependently be a bridging group, W, which is bonded to said R⁵.

In one embodiment, —R⁷ and —R⁸ are each a bridging group, W, which isbonded to said phenyl group R⁵.

In one embodiment, —R⁷ and —R⁸ are each a bridging group, W, which isbonded to said phenyl group R⁵ at an ortho position, relative to thexanthylium core, to produce a six-membered fused ring.

In one embodiment, both —R⁷ and —R⁸ are bridging groups, W, and are eachbonded to said phenyl group R⁵ at respective ortho positions, to producesix-membered fused rings as shown in formula (VI).

Preferences for —R⁹, —R¹⁰, —R¹¹ and —R¹²

—R⁹, —R¹⁰, —R¹¹ and —R¹² are each independently saturated C₂₋₆alkyl.

In one embodiment, —R⁹, —R¹⁰, —R¹¹ and —R¹² are each independentlysaturated C₂₋₆alkyl.

In one embodiment, the C₂₋₆alkyl groups are selected from: linearC₂₋₆alkyl groups, such as -Et, -nPr, -iPr, and -nBu; branched C₃₋₄alkylgroups, such as -iPr, -iBu, -sBu, and -tBu; and cyclic C₃₋₄alkyl groups,such as -cPr and -cBu.

In one embodiment, each —R⁹, —R¹⁰, —R¹¹ and —R¹² is independentlysaturated C₃₋₆cycloalkyl or unsubstituted saturated aliphatic C₂₋₆alkyl.

In one embodiment, each —R⁹, —R¹⁰, —R¹¹ and —R¹² is independentlysaturated C₃₋₆cycloalkyl.

In one embodiment, each —R⁹, —R¹⁰, —R¹¹ and —R¹² is independentlysaturated aliphatic C₂₋₆alkyl.

In one embodiment, each —R⁹, —R¹⁰, —R¹¹ and —R¹² is independentlysaturated aliphatic C₂₋₄alkyl.

In one embodiment each —R⁹, —R¹⁰, —R¹¹ and —R¹² is independentlyselected from -Et; -n-Pr, -iso-Pr, -n-Bu, -sec-Bu, -iso-Bu, and-tert-Bu.

In one embodiment, one of —R⁹ and —R¹⁰ is -Et.

In one embodiment, one of —R¹¹ and —R¹² is -Et.

In one embodiment, —R⁹ and —R¹⁰ are the same.

In one embodiment, —R⁹ and —R¹⁰ are each -Et.

In one embodiment, —R¹¹ and —R¹² are the same.

In one embodiment, —R¹¹ and —R¹² are each -Et.

In one embodiment, —R⁹ and —R¹¹ are the same. In one embodiment —R⁹ and—R¹¹ are each -Et.

In one embodiment, —R¹⁰ and —R¹² are the same. In one embodiment, —R¹⁰and —R¹² are each -Et.

In one embodiment, —R⁹, —R¹⁰, —R¹¹ and —R¹² are the same.

In one embodiment, —R⁹, —R¹⁰, —R¹¹ and —R¹² are each -Et.

In one embodiment, —R⁹ and —R¹⁰, together with the nitrogen atom towhich they are bound, form a saturated C₃₋₇ heterocycle; and —R¹¹ and—R¹², together with the nitrogen atom to which they are bound,independently form a saturated C₃₋₇ heterocycle.

In one embodiment the saturated C₃₋₇ heterocycle formed by R⁹ and R¹⁰and the saturated C₃₋₇ heterocycle formed by R¹¹ and R¹² areindependently selected from: aziridine, azetidine, pyrrolidine,imidazolidine, pyrazolidine, oxazolidine, isoxazolidine, piperidine,piperazine, morpholine, azepine, oxazepine, and diazepine.

In one embodiment the saturated C₃₋₇ heterocycle formed by R⁹ and R¹⁰and the saturated C₃₋₇ heterocycle formed by R¹¹ and R¹² areindependently selected from: morpholine, piperidine, and pyrrolidine.

In one embodiment the saturated C₃₋₇ heterocycle is morpholine.

In one embodiment the saturated C₃₋₇ heterocycle is piperidine.

In one embodiment the saturated C₃₋₇ heterocycle is pyrrolidine.

In one embodiment the saturated C₃₋₇ heterocycle formed by R⁹ and R¹⁰and the saturated C₃₋₇ heterocycle formed by R¹¹ and R¹² are the same.

Preferred Compounds

In general, the present invention relates to one or more compoundsselected from the following compounds, and their use in medicine:

Com- pound Structure and Name A

B

C

D

E

F

G

H

I

I•HNO₃

J

K

L

M

N

O

AB

AC

AD

AE

AF

AG

AH

AI

AJ

AK

AL

AM

AN

In this and all other aspects of the invention, unless context demandsotherwise, a compound may be selected from the list consisting of A, B,C, D, E, F, G, H, I, I.HNO₃, J, K, L, M, N, O, AB, AC, AD, AE, AF, AG,AH, AI, AJ, AK, AL, AM and AN.

In one embodiment, a compound may be selected from the list consistingof A, B, C, D, E, F, G, H, I, I.HNO₃, J, K, L, M, N, and O.

In one embodiment, a compound may be selected from the list consistingof A, B, C, D, E, F, G, H, I, I.HNO₃, and J.

In one embodiment, the compound is selected from list consisting of A,B, C, and D.

In one embodiment, the compound is selected from list consisting of Band D.

In one embodiment, the compound is selected from list consisting of E,F, G, H, I, I.HNO₃, J, and K.

In one embodiment, the compound is selected from list consisting of E,F, G, I, I.HNO₃, J, and K.

In one embodiment, the compound is selected from list consisting of F,I, I.HNO₃, and J.

In one embodiment, the compound is selected from list consisting of L,M, N, and O.

In one embodiment, the compound is selected from list consisting of Nand O.

In one embodiment, the compound is selected from list consisting of K,L, and, M.

In one embodiment, the compound is selected from list consisting of Land M.

In one embodiment, the compound is selected from list consisting of AB,AC, AD, AE, AF, AG, AH, AI, AJ, AK, and AL.

In one embodiment, the compound is selected from the list consisting ofAB, AC, AD, AE, AF, AG, AH, AI, AJ, and AK.

In one embodiment, the compound is selected from the list consisting ofAC and AD.

In one embodiment, the compound is selected from the list consisting ofAF, AG, AH, AI, AJ, and AK.

In one embodiment, the compound is selected from the list consisting ofAF, AG and AH.

In one embodiment, the compound is selected from the list consisting ofAI, AJ, and AK.

In one embodiment, the compound is selected from the list consisting ofAM and AN.

In one embodiment, it is compound A.

In one embodiment, it is compound B.

In one embodiment, it is compound C.

In one embodiment, it is compound D.

In one embodiment, it is compound E.

In one embodiment, it is compound F.

In one embodiment, it is compound G.

In one embodiment, it is compound H.

In one embodiment, it is compound I.

In one embodiment, it is compound I.HNO₃.

In one embodiment, it is compound J.

In one embodiment, it is compound K.

In one embodiment, it is compound L.

In one embodiment, it is compound M.

In one embodiment, it is compound N.

In one embodiment, it is compound O.

In one embodiment, it is compound AB.

In one embodiment, it is compound AC.

In one embodiment, it is compound AD.

In one embodiment, it is compound AE.

In one embodiment, it is compound AF.

In one embodiment, it is compound AG.

In one embodiment, it is compound AH.

In one embodiment, it is compound AI.

In one embodiment, it is compound AJ.

In one embodiment, it is compound AK.

In one embodiment, it is compound AL.

In one embodiment, it is compound AM.

In one embodiment, it is compound AN.

In one embodiment the xanthylium compound may be one which is obtainedby, or is obtainable by, a method as described herein (see “Methods ofSynthesis” below).

Preferred compounds of the present invention are those which show highactivity in the assays described herein, particularly the in vitro assaydescribed below. Preferred compounds have a B50 of less than 500, morepreferably less than 300, 200, 100, 90, 80, 70, 60, 50, or 40 μM, asdetermined with reference to the Examples herein.

In one embodiment the xanthylium compound has a RxIndex (RxI) valueobtained as determined with reference to the Examples herein of greaterthan or equal to 150, more preferably greater than or equal to 200, 250,300, 500, 1000, 1500, or 2000.

The present invention also provides intermediates for use in thepreparation of the compounds of the invention. Such intermediates aredescribed below in the methods of synthesis section

Isotopic Variation

In one embodiment, one or more of the carbon atoms of the compound is¹¹C or ¹³C or ¹⁴C.

In one embodiment, one or more of the carbon atoms of the compound is¹¹C.

In one embodiment, one or more of the carbon atoms of the compound is¹³C.

In one embodiment, one or more of the carbon atoms of the compound is¹⁴C.

In one embodiment, one or more of the nitrogen atoms of the compound is¹⁵N.

In one embodiment, one or more or all of the carbon atoms of one or moreor all of the groups —R¹, —R², —R³, —R⁴, —R⁹, —R¹⁰, R¹¹, and —R¹² is¹¹C.

In one embodiment, the groups —R¹, —R², —R³ and —R⁴ are each —(¹¹CH₂¹¹CH₃).

In one embodiment, the groups —R¹, —R², —R³ and —R⁴ are each —(¹¹CH₃).

In one embodiment, the groups —R⁹, —R¹⁰, —R¹¹ and —R¹² are each —(¹¹CH₂¹¹CH₃).

In one embodiment, one or more or all of the carbon atoms, wherepresent, of the groups —R⁵, —R^(5A), —R⁶, —R⁷, or —R⁸ is ¹¹C.

In one embodiment, one or more or all of the carbon atoms, wherepresent, of the groups —R⁵, —R^(5A), or —R⁶ is ¹¹C.

In one embodiment, one or more or all of the carbon atoms, wherepresent, of the groups —R⁷ or —R⁸ is ¹¹C.

Uses to Reverse or Inhibit the Aggregation of tau Protein.

One aspect of the invention is the use of a xanthylium compound toreverse or inhibit the aggregation of tau protein. This aggregation maybe in vitro, or in vivo, and may be associated with a tauopathy diseasestate as discussed herein. Also provided are methods of reversing orinhibiting the aggregation of tau protein comprising contacting theaggregate or protein with a compound as described herein.

As discussed below, various tauopathy disorders that have beenrecognized which feature prominent tau pathology in neurons and/or gliaand this term has been used in the art for several years. Thesimilarities between these pathological inclusions and thecharacteristic tau inclusions in diseases such as AD indicate that thestructural features are shared and that it is the topographicdistribution of the pathology that is responsible for the differentclinical phenotypes observed. In addition to specific diseases discussedbelow, those skilled in the art can identify tauopathies by combinationsof cognitive or behavioural symptoms, plus additionally through the useof appropriate ligands for aggregated tau as visualised using PET orMRI, such as those described in WO02/075318.

Methods of Treatment or Prophylaxis and 1^(st) & 2^(nd) Medical Uses

One aspect of the present invention pertains to a method of treatment orprophylaxis of a tauopathy condition in a patient, comprisingadministering to said patient a therapeutically-effective amount of axanthylium compound, as described herein.

Aspects of the present invention relate to “tauopathies”. As well asAlzheimer's disease (AD), the pathogenesis of neurodegenerativedisorders such as Pick's disease and Progressive Supranuclear Palsy(PSP) appears to correlate with an accumulation of pathologicaltruncated tau aggregates in the dentate gyrus and stellate pyramidalcells of the neocortex, respectively. Other dementias includefronto-temporal dementia (FTD); parkinsonism linked to chromosome 17(FTDP-17); disinhibition-dementia-parkinsonism-amyotrophy complex(DDPAC); pallido-ponto-nigral degeneration (PPND); Guam-ALS syndrome;pallido-nigro-luysian degeneration (PNLD); cortico-basal degeneration(CBD); Dementia with Argyrophilic grains (AgD); Dementia pugilistica(DP) wherein despite different topography, NFTs are similar to thoseobserved in AD (H of P. R., Bouras C., Buée L., Delacourte A., Perl D.P. and Morrison J. H. (1992) Differential distribution ofneurofibrillary tangles in the cerebral cortex of dementia pugilisticaand Alzheimer's disease cases. Acta Neuropathol. 85, 23-30); Chronictraumatic encephalopathy (CTE), a tauopathy including DP as well asrepeated and sports-related concussion (McKee, A., Cantu, R., Nowinski,C., Hedley-Whyte, E., Gavett, B., Budson, A., Santini, V., Lee, H.-S.,Kubilus, C. & Stern, R. (2009) Chronic traumatic encephalopathy inathletes: progressive tauopathy after repetitive head injury. Journal ofNeuropathology & Experimental Neurology 68, 709-735). Others arediscussed in Wischik et al. 2000, loc. cit, for detaileddiscussion—especially Table 5.1).

Abnormal tau in NFTs is found also in Down's Syndrome (DS) (Flament S.,Delacourte A. and Mann D. M. A. (1990) Phosphorylation of tau proteins:a major event during the process of neurofibrillary degeneration. Acomparative study between AD and Down's syndrome. Brain Res., 516,15-19). Also Dementia with Lewy bodies (DLB) (Harrington, C. R., Perry,R. H., Perry, E. K., Hurt, J., McKeith, I. G., Roth, M. & Wischik, C. M.(1994) Senile dementia of Lewy body type and Alzheimer type arebiochemically distinct in terms of paired helical filaments andhyperphosphorylated tau protein. Dementia 5, 215-228). Tau-positive NFTsare also found in Postencephalitic parkinsonism (PEP) (H of P. R.,Charpiot, A., Delacourte A., Buee, L., Purohit, D., Perl D. P. andBouras, C. (1992) Distribution of neurofibrillary tangles and senileplaques in the cerebral cortex in postencephalitic parkinsonism.Neurosci. Lett. 139, 10-14). Glial tau tangles are observed in Subacutesclerosing panencephalitis (SSPE) (Ikeda K., Akiyama H., Kondo H., AraiT., Arai N. and Yagishita S. (1995) Numerous glial fibrillary tangles inoligodendroglia in cases of Subacute sclerosing panencephalitis withneurofibrillary tangles. Neurosci. Lett., 194, 133-135).

Other tauopathies include Niemann-Pick disease type C (NPC) (Love, S.,Bridges, L. R. & Case, C. P. (1995), Brain, 118, 119-129); Sanfilipposyndrome type B (or mucopolysaccharidosis III B, MPS III B) (Ohmi, K.,Kudo, L. C., Ryazantsev, S., et al. (2009) PNAS, 106, 8332-8337;myotonic dystrophies (DM), DM1 (Sergeant, N., Sablonniere, B.,Schraen-Maschke, S., et al. (2001) Human Molecular Genetics, 10,2143-2155 and references cited therein) and DM2 (Maurage, C. A., Udd,B., Ruchoux, M. M., et al. (2005) Neurology, 65, 1636-1638).

Additionally there is a growing concensus in the literature that a taupathology may also contribute more generally to cognitive deficits anddecline, including in mild cognitive impairment (MCI) (see e.g. Braak,H., Del Tredici, K, Braak, E. (2003) Spectrum of pathology. In Mildcognitive impairment: Aging to Alzheimer's disease edited by Petersen,R. C.; pp. 149-189).

All of these diseases, which are characterized primarily or partially byabnormal tau aggregation, are referred to herein as “tauopathies” or“diseases of tau protein aggregation”.

In this and all other aspects of the invention relating to tauopathies,preferably the tauopathy is selected from the list consisting of theindications above, i.e., AD, Pick's disease, PSP, FTD, FTDP-17, DDPAC,PPND, Guam-ALS syndrome, PNLD, and CBD and AgD, DS, SSPE, DP, PEP, DLB,CTE and MCI.

In one preferred embodiment the tauopathy is Alzheimer's disease (AD).

One aspect of the present invention pertains to a xanthylium compound,as described herein, for use in a method of treatment or prophylaxis(e.g., of a tauopathy condition) of the human or animal body by therapy.

One aspect of the present invention pertains to use of a xanthyliumcompound, as described herein, in the manufacture of a medicament foruse in the treatment or prophylaxis of a tauopathy condition.

A further embodiment is a method of treatment or prophylaxis of adisease of tau protein aggregation as described herein, which methodcomprises administering to a subject a xanthylium compound, ortherapeutic composition comprising the same, such as to inhibit theaggregation of the tau protein associated with said disease state.

Other Methods and Uses

In a further embodiment there is disclosed a xanthylium compound, ortherapeutic composition comprising the same, for use in a method oftreatment or prophylaxis of a disease of tau protein aggregation asdescribed above, which method comprises administering to a subject thexanthylium compound or composition such as to inhibit the aggregation ofthe tau protein associated with said disease state.

In a further embodiment there is disclosed use of a xanthylium compoundin the preparation of a medicament for use in a method of treatment orprophylaxis of a disease of tau protein aggregation as described above,which method comprises administering to a subject the medicament such asto inhibit the aggregation of the tau protein associated with saiddisease state.

In one embodiment there is disclosed a method of regulating theaggregation of a tau protein in the brain of a mammal, which aggregationis associated with a disease state as described above, the treatmentcomprising the step of administering to said mammal in need of saidtreatment, a prophylactically or therapeutically effective amount of aninhibitor of said aggregation, wherein the inhibitor is a xanthyliumcompound.

One aspect of the invention is a method of inhibiting production ofprotein aggregates (e.g. in the form of paired helical filaments (PHFs),optionally in neurofibrillary tangles (NFTs)) in the brain of a mammal,the treatment being as described herein.

In one aspect the invention provides a drug product for the treatment ofa disease state associated with tau protein aggregation in a mammalsuffering therefrom, comprising a container labeled or accompanied by alabel indicating that the drug product is for the treatment of saiddisease, the container containing one or more dosage units eachcomprising at least one pharmaceutically acceptable excipient and, as anactive ingredient, an isolated pure xanthylium compound of theinvention.

Compositions, Formulations and Purity

In one embodiment, the xanthylium compound may be provided or used in acomposition which is equal to or less than 100, 99, 98, 97, 96, 95, 94,93, 92, 91, or 90% pure.

One aspect of the present invention pertains to a dosage unit (e.g., apharmaceutical tablet or capsule) comprising 20 to 300 mg of axanthylium compound as described herein (e.g., obtained by, orobtainable by, a method as described herein; having a purity asdescribed herein; etc.), and a pharmaceutically acceptable carrier,diluent, or excipient.

In one embodiment, the dosage unit is a tablet.

In one embodiment, the dosage unit is a capsule.

Dosage units (e.g., a pharmaceutical tablet or capsule) comprising 20 to300 mg of a xanthylium compound as described herein and apharmaceutically acceptable carrier, diluent, or excipient are discussedin more detail hereinafter.

In one embodiment, the amount is 30 to 200 mg.

In one embodiment, the amount is about 25 mg.

In one embodiment, the amount is about 35 mg.

In one embodiment, the amount is about 50 mg.

In one embodiment, the amount is about 70 mg.

In one embodiment, the amount is about 125 mg.

In one embodiment, the amount is about 175 mg.

In one embodiment, the amount is about 250 mg.

In one embodiment, the pharmaceutically acceptable carrier, diluent, orexcipient is or comprises one or both of a glyceride (e.g., Gelucire44/14®; lauroyl macrogol-32 glycerides PhEur, USP) and colloidal silicondioxide (e.g., 2% Aerosil 200®; Colliodal Silicon Dioxide PhEur, USP).

Formulations

While it is possible for the xanthylium compound to be used (e.g.,administered) alone, it is often preferable to present it as acomposition or formulation.

In one embodiment, the composition is a pharmaceutical composition(e.g., formulation, preparation, medicament) comprising a xanthyliumcompound, as described herein, and a pharmaceutically acceptablecarrier, diluent, or excipient.

In one embodiment, the composition is a pharmaceutical compositioncomprising at least one xanthylium compound, as described herein,together with one or more other pharmaceutically acceptable ingredientswell known to those skilled in the art, including, but not limited to,pharmaceutically acceptable carriers, diluents, excipients, adjuvants,fillers, buffers, preservatives, anti-oxidants, lubricants, stabilisers,solubilisers, surfactants (e.g., wetting agents), masking agents,colouring agents, flavouring agents, and sweetening agents.

In one embodiment, the composition further comprises other activeagents, for example, other therapeutic or prophylactic agents.

Suitable carriers, diluents, excipients, etc. can be found in standardpharmaceutical texts. See, for example, Handbook of PharmaceuticalAdditives, 2nd Edition (eds. M. Ash and I. Ash), 2001 (SynapseInformation Resources, Inc., Endicott, N.Y. , USA), Remington'sPharmaceutical Sciences, 20th edition, pub. Lippincott, Williams &Wilkins, 2000; and Handbook of Pharmaceutical Excipients, 2nd edition,1994.

Another aspect of the present invention pertains to methods of making apharmaceutical composition comprising admixing at least one[¹¹C]-radiolabelled xanthylium or xanthylium-like compound, as definedherein, together with one or more other pharmaceutically acceptableingredients well known to those skilled in the art, e.g., carriers,diluents, excipients, etc. If formulated as discrete units (e.g.,tablets, etc.), each unit contains a predetermined amount (dosage) ofthe active compound.

The term “pharmaceutically acceptable,” as used herein, pertains tocompounds, ingredients, materials, compositions, dosage forms, etc.,which are, within the scope of sound medical judgment, suitable for usein contact with the tissues of the subject in question (g., human)without excessive toxicity, irritation, allergic response, or otherproblem or complication, commensurate with a reasonable benefit/riskratio. Each carrier, diluent, excipient, etc. must also be “acceptable”in the sense of being compatible with the other ingredients of theformulation.

The formulations may be prepared by any methods well known in the art ofpharmacy. Such methods include the step of bringing into association theactive compound with a carrier which constitutes one or more accessoryingredients. In general, the formulations are prepared by uniformly andintimately bringing into association the active compound with carriers(e.g., liquid carriers, finely divided solid carrier, etc.), and thenshaping the product, if necessary.

The formulation may be prepared to provide for rapid or slow release;immediate, delayed, timed, or sustained release; or a combinationthereof.

Formulations suitable for parenteral administration (e.g., byinjection), include aqueous or non-aqueous, isotonic, pyrogen-free,sterile liquids (e.g., solutions, suspensions), in which the activeingredient is dissolved, suspended, or otherwise provided (e.g., in aliposome or other microparticulate). Such liquids may additional containother pharmaceutically acceptable ingredients, such as anti-oxidants,buffers, preservatives, stabilisers, bacteriostats, suspending agents,thickening agents, and solutes which render the formulation isotonicwith the blood (or other relevant bodily fluid) of the intendedrecipient. Examples of excipients include, for example, water, alcohols,polyols, glycerol, vegetable oils, and the like. Examples of suitableisotonic carriers for use in such formulations include Sodium ChlorideInjection, Ringer's Solution, or Lactated Ringer's Injection. Typically,the concentration of the active ingredient in the liquid is from about 1ng/ml to about 10 μg/ml, for example from about 10 ng/ml to about 1μg/ml. The formulations may be presented in unit-dose or multi-dosesealed containers, for example, ampoules and vials, and may be stored ina freeze-dried (lyophilised) condition requiring only the addition ofthe sterile liquid carrier, for example water for injections,immediately prior to use. Extemporaneous injection solutions andsuspensions may be prepared from sterile powders, granules, and tablets.

Dosage

It will be appreciated by one of skill in the art that appropriatedosages of the xanthylium compound, and compositions comprising thexanthylium compound, can vary from patient to patient. Determining theoptimal dosage will generally involve the balancing of the level oftherapeutic benefit against any risk or deleterious side effects. Theselected dosage level will depend on a variety of factors including, butnot limited to, the activity of the particular compound, the route ofadministration, the time of administration, the rate of excretion of thecompound, the duration of the treatment, other drugs, compounds, and/ormaterials used in combination, the severity of the condition, and thespecies, sex, age, weight, condition, general health, and prior medicalhistory of the patient. The amount of compound and route ofadministration will ultimately be at the discretion of the physician,veterinarian, or clinician, although generally the dosage will beselected to achieve local concentrations at the site of action whichachieve the desired effect without causing substantial harmful ordeleterious side-effects.

Administration can be effected in one dose, continuously orintermittently (e.g., in divided doses at appropriate intervals)throughout the course of treatment. Methods of determining the mosteffective means and dosage of administration are well known to those ofskill in the art and will vary with the formulation used for therapy,the purpose of the therapy, the target cell(s) being treated, and thesubject being treated. Single or multiple administrations can be carriedout with the dose level and pattern being selected by the treatingphysician, veterinarian, or clinician.

In general, a suitable dose of the active compound is in the range ofabout 100 ng to about 25 mg (more typically about 1 μg to about 10 mg)per kilogram body weight of the subject per day. Where the activecompound is a salt, an ester, an amide, a prodrug, or the like, theamount administered is calculated on the basis of the parent compoundand so the actual weight to be used is increased proportionately.

In one embodiment, the active compound is administered to a humanpatient according to the following dosage regime: about 100 mg, 3 timesdaily.

In one embodiment, the active compound is administered to a humanpatient according to the following dosage regime: about 150 mg, 2 timesdaily.

In one embodiment, the active compound is administered to a humanpatient according to the following dosage regime: about 200 mg, 2 timesdaily.

However in one embodiment, the xanthylium compound is administered to ahuman patient according to the following dosage regime: about 50 orabout 75 mg, 3 or 4 times daily.

In one embodiment, the xanthylium compound is administered to a humanpatient according to the following dosage regime: about 100 or about 125mg, 2 times daily.

Preferred Combination Therapies

Combination treatments and therapies, in which two or more treatments ortherapies are combined, for example, sequentially or simultaneously, arediscussed in more detail hereinafter. Thus it will be understood thatany of the medical uses or methods described herein may be used in acombination therapy.

In one embodiment, a treatment of the invention (e.g., employing acompound of the invention) is in combination with a cholinesteraseinhibitor such as donepezil (Aricept™) rivastigmine (Exelon™) orgalantamine (Reminyl™).

In one embodiment, a treatment of the invention (e.g., employing acompound of the invention) is in combination with an NMDA receptorantagonist such as memantine (Ebixa™, Namenda™).

In one embodiment, a treatment of the invention (e.g. employing acompound of the invention) is in combination with a muscarinic receptoragonist.

In one embodiment, a treatment of the invention (e.g. employing acompound of the invention) is in combination with an inhibitor ofamyloid precursor protein to beta-amyloid (e.g., an inhibitor of amyloidprecursor protein processing that leads to enhanced generation ofbeta-amyloid).

Ligands and Labels

Xanthylium compounds discussed herein that are capable of inhibiting theaggregation of tau protein will also be capable of acting as ligands orlabels of tau protein (or aggregated tau protein). Thus, in oneembodiment, the xanthylium compound is a ligand of tau protein (oraggregated tau protein).

Such xanthylium compounds (ligands) may incorporate, be conjugated to,be chelated with, or otherwise be associated with, other chemicalgroups, such as stable and unstable detectable isotopes, radioisotopes,positron-emitting atoms, magnetic resonance labels, dyes, fluorescentmarkers, antigenic groups, therapeutic moieties, or any other moietythat may aid in a prognostic, diagnostic or therapeutic application.

For example, as noted above, in one embodiment, the xanthylium compoundis as defined above, but with the additional limitation that thecompound incorporates, is conjugated to, is chelated with, or isotherwise associated with one or more (e.g., 1, 2, 3, 4, etc.) isotopes,radioisotopes, positron-emitting atoms, magnetic resonance labels, dyes,fluorescent markers, antigenic groups, or therapeutic moieties.

In one embodiment, the xanthylium compound is a ligand as well as alabel, e.g., a label for tau protein (or aggregated tau protein), andincorporates, is conjugated to, is chelated with, or is otherwiseassociated with, one or more (e.g., 1, 2, 3, 4, etc.) detectable labels.

For example, in one embodiment, the xanthylium compound is as definedabove, but with the additional limitation that the compoundincorporates, is conjugated to, is chelated with, or is otherwiseassociated with, one or more (e.g., 1, 2, 3, 4, etc.) detectable labels.

Labelled xanthylium compounds (e.g., when ligated to tau protein oraggregated tau protein) may be visualised or detected by any suitablemeans, and the skilled person will appreciate that any suitabledetection means as is known in the art may be used.

For example, the xanthylium compound (ligand-label) may be suitablydetected by incorporating a positron-emitting atom (e.g., ¹¹C) (e.g., asa carbon atom of one or more alkyl group substituents, e.g., methylgroup substituents) and detecting the compound using positron emissiontomography (PET) as is known in the art.

Treatment

The term “treatment,” as used herein in the context of treating acondition, pertains generally to treatment and therapy, whether of ahuman or an animal (e.g., in veterinary applications), in which somedesired therapeutic effect is achieved, for example, the inhibition ofthe progress of the condition, and includes a reduction in the rate ofprogress, a halt in the rate of progress, regression of the condition,amelioration of the condition, and cure of the condition. Treatment as aprophylactic measure (i.e., prophylaxis, prevention) is also included.

The term “therapeutically-effective amount,” as used herein, pertains tothat amount of an active compound, or a material, composition or dosagefrom comprising an active compound, which is effective for producingsome desired therapeutic effect, commensurate with a reasonablebenefit/risk ratio, when administered in accordance with a desiredtreatment regimen.

Similarly, the term “prophylactically-effective amount,” as used herein,pertains to that amount of an active compound, or a material,composition or dosage from comprising an active compound, which iseffective for producing some desired prophylactic effect, commensuratewith a reasonable benefit/risk ratio, when administered in accordancewith a desired treatment regimen.

The term “treatment” includes combination treatments and therapies, inwhich two or more treatments or therapies are combined, for example,sequentially or simultaneously. Examples of treatments and therapiesinclude, but are not limited to, chemotherapy (the administration ofactive agents, including, e.g., drugs, antibodies (e.g., as inimmunotherapy), prodrugs (e.g., as in photodynamic therapy, GDEPT,ADEPT, etc.); surgery; radiation therapy; and gene therapy.

Routes of Administration

The xanthylium compound, or pharmaceutical composition comprising it,may be administered to a subject/patient by any convenient route ofadministration, whether systemically/peripherally or topically (i.e., atthe site of desired action).

Routes of administration include, but are not limited to, oral (e.g., byingestion); buccal; sublingual; transdermal (including, e.g., by apatch, plaster, etc.); transmucosal (including, e.g., by a patch,plaster, etc.); intranasal (e.g., by nasal spray); ocular (e.g., byeyedrops); pulmonary (e.g., by inhalation or insufflation therapy using,e.g., via an aerosol, e.g., through the mouth or nose); rectal (e.g., bysuppository or enema); vaginal (e.g., by pessary); parenteral, forexample, by injection, including subcutaneous, intradermal,intramuscular, intravenous, intraarterial, intracardiac, intrathecal,intraspinal, intracapsular, subcapsular, intraorbital, intraperitoneal,intratracheal, subcuticular, intraarticular, subarachnoid, andintrasternal (including, e.g., intracatheter injection into the brain);by implant of a depot or reservoir, for example, subcutaneously orintramuscularly.

The Subject/Patient

The subject/patient may be an animal, mammal, a placental mammal, amarsupial (e.g., kangaroo, wombat), a monotreme (e.g., duckbilledplatypus), a rodent (e.g., a guinea pig, a hamster, a rat, a mouse),murine (e.g., a mouse), a lagomorph (e.g., a rabbit), avian (e.g., abird), canine (e.g., a dog), feline (e.g., a cat), equine (e.g., ahorse), porcine (e.g., a pig), ovine (e.g., a sheep), bovine (e.g., acow), a primate, simian (e.g., a monkey or ape), a monkey (e.g.,marmoset, baboon), an ape (e.g., gorilla, chimpanzee, orangutang,gibbon), or a human.

Furthermore, the subject/patient may be any of its forms of development,for example, a foetus.

In one preferred embodiment, the subject/patient is a human.

Suitable subjects for the method may be selected on the basis ofconventional factors. Thus the initial selection of a patient mayinvolve any one or more of: rigorous evaluation by experiencedclinician; exclusion of non-AD diagnosis as far as possible bysupplementary laboratory and other investigations; objective evaluationof level of cognitive function using neuropathologically validatedbattery.

In one embodiment, the subject/patient is not a human.

The invention will now be further described with reference to thefollowing non-limiting Examples. Other embodiments of the invention willoccur to those skilled in the art in the light of these.

The disclosure of all references cited herein, inasmuch as it may beused by those skilled in the art to carry out the invention, is herebyspecifically incorporated herein by cross-reference.

Methods of Synthesis

Methods for the chemical synthesis of compounds of the present inventionare described in the Examples herein. These and/or other well knownmethods may be modified and/or adapted in known ways in order tofacilitate the synthesis of other compounds of the present invention.

Thus one aspect of the invention provides a method of synthesising acompound of the invention as described herein, described, orsubstantially as described, with reference to any of the Exampleshereinafter.

The invention further provides a xanthylium compound of the inventionwhich is obtained by or is obtainable by, a method as described herein.

One aspect of the present invention pertains to methods for thepreparation of xanthylium compounds, as described herein.

The present invention also provides intermediate compounds for use inthe preparation of the compounds of the invention.

Compounds (IVa) and (IVb)

The compounds of formula (Ic) may be prepared from a compound of formula(IVa) and the salts thereof, the compounds of formula (I) may beprepared from a compound of formula (IVd) and the salts thereof, and thecompounds of formula (IIa) and (III) may be prepared from the compoundof formula (IVb) and the salts thereof:

-   -   wherein substituents —R⁵, —R⁹ to —R¹², —R^(13a), —R^(13b),        —R^(14a), —R^(14b), —R^(15a), —R^(15b), —R^(16a), and —R^(16b)        are as defined for the compounds of formula (I), (Ic), (IIa)        and (III) as appropriate.

In one aspect of the invention there is provided a compound of formula(IVa) and salts thereof, where —R⁵ is saturated C₁₋₆alkyl, which isunsubstituted or substituted with one or more substituents —R^(5A), and—R^(5A) is as defined for the compounds of formula (I).

In one embodiment, there is provided a compound of formula (IVa) withthe proviso that —R⁵ is not —CF₃.

In another aspect of the invention there is provided a compound offormula (IVb) and salts thereof, where —R⁹ to —R¹² are defined accordingto the compounds of formula (IIa) and (III), and —R⁵ is saturatedC₁₋₆alkyl, which is unsubstituted or substituted with one or moresubstituents —R^(5A), where —R^(5A) is as defined for the compounds offormula (IIa) and (III).

In one aspect of the invention there is provided a method of preparing acompound of formula (IVa), the method comprising the step of reacting amixture of 8-hydroxyjulolidine and a compound R⁵—CHO in a solvent atroom temperature or above, wherein —R⁵ is as defined for the compoundsof formula (IVa).

In another aspect of the invention there is provided a method ofpreparing a compound of formula (IVb) from a compound of formula (V):

-   -   wherein —R¹³ and —R¹⁴ are each independently saturated        C₁₋₆alkyl.

In one embodiment, —R¹³ and —R¹⁴ are each independently saturatedC₂₋₆alkyl.

In one embodiment, the C₂₋₆alkyl groups are selected from: linearC₂₋₆alkyl groups, such as -Et, -nPr, -iPr, and -nBu; branched C₃₋₄alkylgroups, such as -iPr, -iBu, -sBu, and -tBu; and cyclic C₃₋₄alkyl groups,such as -cPr and -cBu.

In one embodiment, each —R¹³ and —R¹⁴ is independently saturatedaliphatic C₁₋₄alkyl.

In one embodiment, each —R¹³ and —R¹⁴ is independently saturatedaliphatic C₂₋₄alkyl.

In one embodiment each —R¹³ and —R¹⁴ is independently selected from -Me,-Et; -n-Pr, -iso-Pr, -n-Bu, -sec-Bu, -iso-Bu, and -tert-Bu.

In one embodiment, —R¹³ and —R¹⁴ are the same.

In one embodiment, —R¹³ and —R¹⁴ are each -Et. In one embodiment, —R¹³and —R¹⁴ are each -Me.

The method comprises the step of reacting a mixture of a compound offormula (V) and a compound R⁵—CHO in a solvent at room temperature orabove, wherein —R⁵ is as defined for the compounds of formula (IVb).

The preferences for —R⁵ for the compounds of formula (I) are alsoapplicable to the compounds of formula (IVa) and (IVb), and compoundR⁵—CHO, where appropriate.

Where —R⁵ is —H, the compound R⁵—CHO is formalin. Where —R⁵ is -Et, thecompound R⁵—CHO is propionaldehyde.

In the methods described above, the reaction may be performed at 35° C.or above, 40° C. or above, 50° C. or above, or 55° C. or above.

In one embodiment, the temperature may be performed at ±2° C. of thetemperature specified.

The solvent may be a C₁₋₄alkyl alcohol. The solvent may be methanol orethanol.

The reaction may be performed in the presence of an acid. Preferably theacid is hydrochloric acid. In one embodiment, the compounds of formula(IVa) and (IVb) may be obtained as hydrochloride salts.

In one embodiment, the method further comprises the step of addingsufficient base to the product of the reaction such that the resultingmixture has a pH of 7 or more. In one embodiment the compounds offormula (IVa) and (IVb) may be obtained as a free base.

Compound P

In one embodiment, there is provided a method of preparing a compound Pand the salts thereof, the method comprising the step of reacting amixture of 8-hydroxyjulolidine and formalin in a solvent at roomtemperature or above.

The solvent may be methanol.

The reaction mixture may be heated to reflux.

The reaction may be performed at 35° C. or above, 40° C. or above, 50°C. or above, or 55° C. or above.

In one embodiment the reaction is performed at 55° C. or above.

In one embodiment the temperature may be performed at ±2° C. of thetemperature specified.

The reaction may be performed in the presence of an acid. Preferably theacid is hydrochloric acid. In one embodiment, compound P may be obtainedas a hydrochloride salt.

In one embodiment, the method further comprises the step of addingsufficient base to the product of the reaction such that the resultingmixture has a pH of 7 or more. In one embodiment, compound P may beobtained as a free base.

Compound P finds use as an intermediate in the synthesis of compounds Aand B. In one aspect of the methods described herein, the hydrochloridesalt of compound P finds use in the synthesis of compounds of formula(I), and preferably the synthesis of compounds A and B.

The method described herein provides a greater yield of compound P thandescribed previously in U.S. Pat. No. 3,932,415. The present method hasa yield of 81%, whilst the method described in U.S. Pat. No. 3,932,415is said to have a yield of 68%. Furthermore, compound P may be obtainedsubstantially free of impurities in the present method without the needfor column chromatography in contrast to the method of U.S. Pat. No.3,932,415.

Compound Q

The present invention provides an intermediate compound Q and the saltsthereof:

Compound Q finds use as an intermediate in the synthesis of compound D.

In one embodiment, there is provided a method of preparing a compound offormula Q and the salts thereof, the method comprising the step ofreacting a mixture of 8-hydroxyjulolidine and propionaldehyde in asolvent at room temperature or above.

The solvent may be ethanol.

The reaction may be performed at about 35° C. or above, or about 40° C.or above. In one embodiment the reaction is performed at about 40° C. orabove.

In one embodiment the reaction may be performed at ±2° C. of thetemperature specified.

The reaction may be performed in the presence of an acid. Preferably theacid is hydrochloric acid. In one embodiment, compound Q may be obtainedas a hydrochloride salt.

In one embodiment, the method further comprises the step of addingsufficient base to the product of the reaction such that the resultingmixture has a pH of 7 or more. In one embodiment, compound Q may beobtained as a free base.

Compound R

The present invention provides an intermediate compound R and the saltsthereof:

Compound R finds use as an intermediate in the synthesis of compound J.

In one embodiment, there is provided a method of preparing a compound offormula R and the salts thereof, the method comprising the step ofreacting a mixture of 3-diethylaminophenol and propionaldehyde in asolvent at room temperature or above.

The solvent may be methanol.

The reaction may be performed at about 35° C. or above, or about 40° C.or above.

In one embodiment the reaction is performed at about 40° C. or above.

In one embodiment the reaction may be performed at ±2° C. of thetemperature specified.

The reaction may be performed in the presence of an acid. Preferably theacid is hydrochloric acid. In one embodiment, compound R may be obtainedas a hydrochloride salt.

In one embodiment, the method further comprises the step of addingsufficient base to the product of the reaction such that the resultingmixture has a pH of 7 or more. In one embodiment, compound R may beobtained as a free base.

Compounds (I), (IIa) or (III)

In one aspect of the invention there is provided a method of preparing acompound of formula (I), (IIa) or (III), the method comprising the stepsof (i) reacting a compound of formula (IVa) or (IVb) with acid; and (ii)subsequently adding sufficient base to the reaction mixture such thatthe resulting mixture has a pH of 7 or more.

The compound of formula (IVa) may be used to prepare compounds offormula (I). The compound of formula (IVb) may be used to preparecompounds of formula (II) and (III).

The acid may be sulfuric acid.

Step (i) may comprise reacting a compound of formula (IVa) or (IVb) withacid at 40° C. or above, 60° C. or above, or 80° C. or above.

Step (ii) may comprise adding sufficient base to the reaction mixturesuch that the resulting mixture has a pH of 8 or more, or 9 or more.

Step (ii) may comprise adding sufficient base to the reaction mixturesuch that the resulting mixture has a pH of around 7-8.

Step (ii) may comprise adding sufficient sodium hydroxide to thereaction mixture such that the resulting mixture has a pH of 7 or more.The sodium hydroxide may be an aqueous solution.

During the addition of the base, the mixture may be maintained at atemperature of 20° C. or below.

The method described herein may provide a greater yield of the product,compared to the reactions that have been previously described in theart.

In another aspect of the invention there is provided a method ofpreparing a compound of formula (I), (IIa) or (III), the methodcomprising the steps of (i) reacting a compound of formula (IVa) or(IVb) with acid; and (ii) subsequently adding an oxidant to the productof step (i).

In step (ii) the oxidant is independently selected from nitric acid,chloranil, benzoquinone, DDQ, sodium hypochlorite, hydrogen peroxide,potassium permanganate, chromium-containing oxidants, manganese dioxide,sodium nitrite, isopentyl nitrite, tert-butyl nitrite and FeCl₃. In oneembodiment, the oxidant is nitric acid. In another embodiment theoxidant is FeCl₃. The inventors have established that use of the oxidantFeCl₃ allows the preparation of product having a greater purity comparedto the products produced using other oxidants.

In one embodiment, step (i) comprises the step of (i) reacting acompound of formula (IVa) or (IVb) with acid and subsequently addingsufficient base to the reaction mixture such that the resulting mixturehas a pH of 7 or more.

In one aspect of the invention there is provided a method for thepreparation of compounds formula (I), (IIa) or (III) where X is NO₃ ⁻,the method comprising the steps of (i) reacting a compound of formula(IVa) or (IVb) with acid and, and then treating the product with FeCl₃and optionally an acid, and (ii) subsequently adding nitric acid to theproduct of step (i).

It has been found that the addition of nitric acid to the irontetrachloride product formed in this step (i) provides compounds (I),(IIa) or (III) with low levels of iron. Excessive levels of iron aregenerally unacceptable in pharmaceutical products. It has also beenestablished such compounds may be produced having low levels of otherpharmaceutically unacceptable metals such as lead, aluminium, andmercury.

Compound A or Compound B

In one aspect of the invention there is provided a method of preparingcompound A or compound B, the method comprising the steps of: (i)reacting compound P with acid; and (ii) subsequently adding sufficientbase to the reaction mixture such that the resulting mixture has a pH of7 or more.

The preferences for the method for the preparation of compounds offormula (I) described above, also apply to the methods for thepreparation of compounds A and B, where appropriate.

The method described herein may provides a greater yield of compound Athan described previously in U.S. Pat. No. 3,932,415. The present methodhas a yield of 52%, whilst the method described in U.S. Pat. No.3,932,415 gives 33%.

Compound E, Compound F, Compound H or Compound I

In one aspect of the invention there is provided a method of preparingcompound E, compound F, compound H, or compound I, the method comprisingthe steps of: (i) reacting a compound of formula (IVb) with acid; and(ii) adding sufficient base to the reaction mixture such that theresulting mixture has a pH of 7 or more.

The preferences for the method for the preparation of compounds offormula (IIa) described above, also apply to the methods for thepreparation of compounds E, F, H, and I, where appropriate.

Compound AB, Compound AC, Compound AD, Compound AF, Compound AG,Compound AH, Compound AI, Compound AJ, and Compound AK

In one aspect of the invention there is provided a method of preparingcompound AB, compound AC, compound AD, compound AF, compound AG,compound AH, compound AI, compound AJ, and compound AK, the methodcomprising the steps of: (i) reacting a compound of formula (IVb) withacid; and (ii) adding sufficient base to the reaction mixture such thatthe resulting mixture has a pH of 7 or more.

The preferences for the method for the preparation of compounds offormula (IIa) described above, also apply to the methods for thepreparation of compounds AB, AC, AD, AF, AG, AH, AI, AJ, and AK, whereappropriate.

Compound (Ia)

In one aspect of the invention there is provided a method of preparing acompound of formula (Ia):

-   -   wherein —R⁵ is as defined according to the compounds of formula        (I), the method comprising the steps of (i) reacting a compound        of formula (IVa) with acid; and (ii) subsequently adding an        oxidant to the product of step (i).

The acid may be sulfuric acid.

Step (i) may comprise reacting a compound of formula (IVa) with acid at40° C. or above, 60° C. or above, or 80° C. or above.

Step (i) may comprise reacting a compound of formula (IVa) with acidthen adding sufficient base to the reaction mixture such that theresulting mixture has a pH of 7 or more. Sufficient base may be added tothe reaction mixture such that the resulting mixture has a pH of 8 ormore, or 9 or more. The step may comprise adding sufficient sodiumhydroxide to the reaction mixture such that the resulting mixture has apH of 7 or more. The sodium hydroxide may be an aqueous solution.

During the addition of the base, the mixture may be maintained at atemperature of 20° C. or below.

In step (ii), the oxidant is preferably nitric acid or FeCl₃.

In step (ii), nitric acid may be added to the product of step (i), andthe resulting solid may be isolated from the reaction mixture.

In step (ii), nitric acid may be added to the product of step (i), andthe resulting mixture heated to 40° C. or above, or 50° C. or above.

The resulting solid may be further treated with nitric acid and thesolid product may be isolated from the reaction mixture.

Compound B

In one aspect of the invention there is provided a method of preparingcompound B, the method comprising the steps of: (i) reacting compound Pwith acid; and (ii) subsequently adding nitric acid to the product ofstep (i).

The preferences for the method for the preparation of compounds offormula (Ia) described above, also apply to the methods for thepreparation of compound B, where appropriate.

Compound (Ib)

In one aspect of the invention there is provided a method of preparing acompound of formula (Ib) from a compound of formula (IVc).

The compound of formula (Ib) is represented thus:

-   -   wherein —R⁵ is independently saturated C₁₋₆alkyl, which is        unsubstituted or substituted with one or more substituents        —R^(5A), where —R^(5A) is as defined according to the compounds        of formula (I).

The compound of formula (IVc) is represented thus:

-   -   wherein —R⁵ is independently saturated C₁₋₆alkyl, which is        unsubstituted or substituted with one or more substituents        —R^(5A), where —R^(5A) is as defined according to the compounds        of formula (I).

The method comprises the steps of (i) reacting a compound of formula(IVc) with acid; and (ii) adding sufficient base to the reaction mixturesuch that the resulting mixture has a pH of 7 or more; then (iii)subsequently adding hydrochloric acid and sodium nitrite to the reactionmixture,

The acid may be sulfuric acid.

Step (ii) may comprise adding sufficient base to the reaction mixturesuch that the resulting mixture has a pH of 8 or more, or 9 or more.

Step (ii) may comprise adding sufficient base to the reaction mixturesuch that the resulting mixture has a pH of around 7-8.

Step (ii) may comprise adding sufficient sodium hydroxide to thereaction mixture such that the resulting mixture has a pH of 7 or more.The sodium hydroxide may be an aqueous solution.

Compound D

In one aspect of the invention there is provided a method of preparingcompound D, the method comprising the steps of: (i) reacting7,7′-propylidinebis(2,3,6,7-tetrahydrobenzo[i,j]quinolizine-8,8′-diol)with acid; and (ii) adding sufficient base to the reaction mixture suchthat the resulting mixture has a pH of 7 or more; then (iii)subsequently adding hydrochloric acid and sodium nitrite to the reactionmixture,

The preferences for the method for the preparation of compounds offormula (Ib) described above, also apply to the methods for thepreparation of compound D, where appropriate.

Compound (Ie)

In one aspect of the invention there is provided a method of preparing acompound of formula (Ie) from a compound of formula (IVe).

The compound of formula (Ie) is represented thus:

-   -   wherein —R⁵ is as defined according to the compounds of formula        (I).

The compound of formula (IVe) is represented thus:

-   -   wherein —R⁵ is as defined according to the compounds of formula        (I).

The method comprises the steps of (i) reacting a compound of formula(IVe) with acid; and (ii) subsequently adding an oxidant to the productof step (i).

The acid may be sulfuric acid.

Step (i) may comprise reacting a compound of formula (IVe) with acid at40° C. or above, 50° C. or above, or 65° C. or above.

Step (i) may comprise reacting a compound of formula (IVe) with acidthen neutralizing the reaction mixture. Sufficient base may be added tothe reaction mixture such that the resulting mixture has a pH of 7 ormore, 8 or more, or 9 or more. The step may comprise adding sufficientsodium hydroxide to the reaction mixture such that the resulting mixturehas a pH of 7 or more. The sodium hydroxide may be an aqueous solution.

During the addition of the base, the mixture may be maintained at atemperature of 20° C. or below, or 18° C. or below.

In step (ii), the oxidant comprises FeCl₃.

In step (ii), the oxidant may be added to the product of step (i), andthe resulting solid may be isolated from the reaction mixture.

The resulting solid may be further treated with nitric acid and thesolid product may be isolated from the reaction mixture.

Compound AE

In one aspect of the invention there is provided a method of preparingcompound AE, the method comprising the steps of: (i) reacting1,1,7,7,-tetramethyl-8-hydroxyjulolidine with acid; and (ii)subsequently adding sufficient base to the reaction mixture such thatthe resulting mixture has a pH of 7 or more.

The preferences for the method for the preparation of compounds offormula (I) described above, also apply to the methods for thepreparation of compounds AE, where appropriate.

Compound (IId)

In one aspect of the invention there is provided a method of preparing acompound of formula (IId) from a compound of formula (IVb).

The compound of formula (IId) is represented thus:

-   -   wherein    -   X⁻ is a counter ion selected from Cl⁻, Br⁻ and NO₃ ⁻;    -   —R⁹, —R¹⁰, —R¹¹ and —R¹² are as defined according to the        compounds of formula (IIa), the method comprising the steps        of (i) reacting a compound of formula (III) with acid; and (ii)        subsequently adding hydrochloric acid, hydrobromic acid or        nitric acid to the product of step (i);    -   with the proviso that where X⁻ is Cl⁻, —R⁵ is not —H.

In one embodiment, the method comprises the step of preparing a compoundof formula (IId) where the group —R⁵ is independently saturatedC₁₋₆alkyl, which is unsubstituted or substituted with one or moresubstituents —R^(5A).

In one embodiment X⁻ is a counter ion selected from Br⁻ and NO₃ ⁻.Consequently step (ii) comprises subsequently adding hydrobromic acid ornitric acid to the product of step (i).

In step (ii) hydrobromic acid may be used to generate a product where X⁻is Br⁻. Step (ii) may comprise subsequently adding hydrobromic acid tothe product of step (i), and then adding an alkali metal nitrite to thesubsequent mixture. The alkali metal nitrite may be sodium nitrite.

In the embodiment above, step (ii) comprises subsequently addinghydrobromic acid to the product of step (i). Alternatively, step (ii)comprises subsequently nitric acid to the product of step (i), and thensubsequently treating with product with KBr. In this embodiment, themethod comprises the step of (i) reacting a compound of formula (III)with acid, and then subsequently treating the product with FeCl₃ andoptionally an acid.

Step (i) may comprise reacting a compound of formula (III) with sulfuricacid.

Step (i) may comprise reacting a compound of formula (III) with acidthen subsequently adding sufficient base to the reaction mixture suchthat the resulting mixture has a pH of 7 or more. The base may be sodiumhydroxide. During the addition of the base, the mixture may bemaintained at a temperature of 20° C. or below.

In step (ii) nitric acid may be used to generate a product where X⁻ isNO₃ ⁻.

In an alternative embodiment, the method comprises the step of (i)reacting a compound of formula (III) with acid, and then subsequentlytreating the product with FeCl₃ and optionally an acid. The acid may behydrochloric acid. Step (ii) comprises subsequently adding nitric acidto the product of step (i).

As noted above, It has been found that the addition of nitric acid tothe iron tetrachloride product formed in this step (i) provides compound(IId) with low levels of iron and other metals.

In step (ii) hydrochloric acid may be used to generate a product whereX⁻ is Cl⁻. Step (ii) may comprise subsequently adding hydrochloric acidto the product of step (i), and then adding an alkali metal nitrite tothe subsequent mixture. The alkali metal nitrite may be sodium nitrite.

Compound F, Compound I or Compound J

In one aspect of the invention there is provided a method of preparingcompound F or compound I, the method comprising the steps of: (i)reacting 5,5′-bis-diethylamino-2,2′-methandiyl-di-phenol or5,5′-bis-diethylamino-2,2′-propylidine-di-phenol with acid; and (ii)subsequently adding hydrobromic acid, nitric acid or hydrochloric acidto the product of step (i).

The preferences for the method for the preparation of compounds offormula (IId) described above, also apply to the methods for thepreparation of compounds F, I or J, where appropriate.

Compound (IIe)

In an alternative aspect of the invention, there is provided a method ofpreparing a compound of formula (IIe) from a compound of formula (IVb),wherein the compound of formula (IIe) is as defined according to thecompound of formula (IId) except that X is FeCl₄ ⁻.

The method comprising the steps of (i) reacting a compound of formula(III) with acid; and (ii) subsequently adding FeCl₃ to the product ofstep (i).

Step (i) may comprise reacting a compound of formula (III) with sulfuricacid.

Compound (IIb)

The present invention provides methods of preparing compounds of formula(IIb) as described herein.

Compound M

In one aspect of the invention there is provided a method of preparingcompound M, the method comprising the step of reacting4,4′-bis(dimethylamino)diphenylmethane with sulfur and acid.

The acid in step (i) may be sulfuric acid.

In step (i), the sulfur may be added to the acid, followed subsequentlyby addition of 4,4′-bis(dimethylamino)diphenylmethane to the reactionmixture. The reaction mixture may be kept at 5° C. prior to addition ofbis(dimethylamino)diphenylmethane. The reaction mixture may bemaintained at 20° C. or below during addition ofbis(dimethylamino)diphenylmethane.

The method may comprise the additional step of (ii) subsequently addingzinc chloride to the product of step (i).

EXAMPLES Example 1 Methods of Synthesis

The following syntheses are provided solely for illustrative purposesand are not intended to limit the scope of the invention, as describedherein.

Synthesis 12,3,6,7,12,13,16,17-Octahydro-1H,5H,11H,15H-diquinolizino[1,9-bc:1′,9′-hi]xanthyliumchloride

Method A—From U.S. Pat. No. 3,932,415

7,7′-Methylenebis(2,3,6,7-tetrahydrobenzo[i,j]quinolizine-8,8′-diol)

Hydrochloric acid (0.8 cm³, 32%) was added drop wise to a solution of8-hydroxyjulolidine (3.00 g, 15.9 mmol) in methanol (16 cm³) at 5° C.Formalin (0.593 cm³, 40% in water) was then added to the reaction andthe resulting mixture was allowed to stand overnight at 5° C. Themixture was then poured into water (50 cm³) before being neutralisedwith a saturated solution of sodium bicarbonate. The mixture wasextracted with chloroform (3×40 cm³), the combined extracts were driedover sodium sulphate, filtered and the solvent removed under reducedpressure. Column chromatography (3:7 ethyl acetate/hexane) gave thetarget material as a colourless solid (2.11 g, 68%).

δ_(H) (250 MHz, CDCl₃): 6.68 (2H, s, CH), 3.64 (2H, s, CH₂), 3.00 (8H,t, J₁=6 Hz, CH₂), 2.67 (4H, J=6 Hz, CH₂), 2.60 (4H, t, J₂=7 Hz, CH₂),1.97-1.90 (8H, m, CH₂);

_(c) (100 MHz, CDCl₃): 149.3, 142.7, 127.6, 114.6, 114.5, 108.5, 50.2,49.4, 30.9, 27.0, 22.5, 21.7, 21.2; ν_(max) (KBr)/cm⁻¹: 3431, 2927,2853, 2842, 1618, 1494, 1450, 1350, 1332, 1310, 1281, 1270, 1153, 1132;m/z (ESI): 389.3 (100%, [M−H]⁺).

2,3,6,7,12,13,16,17-Octahydro-1H,5H,11H,15H-diquinolizino[1,9-bc;1′,9′-hi]xanthyliumchloride

7,7′-Methylenebis(2,3,6,7-tetrahydrobenzo[i,j]quinolizine-8,8′-diol)(630 mg, 1.62 mmol) was added to concentrated sulphuric acid (2.5 cm³)at 25° C. The resulting solution was heated to 95° C. for 3 hours. Thereaction was allowed to cool to room temperature before being pouredonto ice (15 cm³). The pH of the solution was adjusted to pH 5 withsodium hydroxide (40%) whilst maintaining the temperature below 15° C.Hydrochloric acid (1 cm³, 32%) was added and the reaction temperaturewas then allowed to rise to room temperature. A solution of sodiumnitrite (222 mg, 3.23 mmol) in water (10 cm³) was added drop wise withstirring and the reaction allowed to stand for 20 hours. The solutionwas then saturated with sodium chloride before being extracted withchloroform (6×30 cm³). The combined extracts were dried over sodiumsulphate, filtered and the solvent removed under reduced pressure togive the target material as a green solid (214 mg, 33%).

Method B

7,7′-Methylenebis(2,3,6,7-tetrahydrobenzo[i,j]quinolizine-8,8′-diol)dihydrochloride

Hydrochloric acid (1 cm³, 32%) was added drop wise to a solution of8-hydroxyjulolidine (3.51 g, 18.57 mmol) in methanol (17.5 cm³) at 5° C.Formalin (0.72 cm³, 40% in water) was then added to the reaction and theresulting mixture was heated to 60° C. for 6 hours. Hydrochloric acid (1cm³, 32%) was added to the mixture, prior to cooling to roomtemperature. The product was then collected by filtration, washed withcold methanol (2×5 cm³) and dried under vacuum overnight to give thetarget material as a colourless solid (3.49 g, 81%).

δ_(H) (250 MHz, D₂O): 6.76 (2H, s, CH), 3.76 (2H, s, CH₂), 3.46-3.38(8H, m, CH₂), 2.78-2.72 (8H, m, CH₂), 2.10-2.04 (8H, m, CH₂); ν_(max)(KBr)/cm⁻¹: 3463, 2930, 1634, 1477, 1435, 1306, 1224, 1095; m/z (ESI):391.3 (89%, [M−HCl₂]⁺), 196.7 (100%).

2,3,6,7,12,13,16,17-Octahydro-1H,5H,11H,15H-diquinolizino[1,9-bc;1′,9′-hi]xanthylium chloride

7,7′-Methylenebis(2,3,6,7-tetrahydrobenzo[i,j]quinolizine-8,8′-diol)dihydrochloride (1.00 g, 2.15 mmol) was added to concentrated sulphuricacid (4 cm³) at 25° C. The resulting solution was heated to 90° C. for 3hours. The reaction was allowed to cool before being poured onto ice (5cm³). The pH of the solution was adjusted to pH 9 with sodium hydroxide(40%) whilst maintaining a temperature below 15° C. Hydrochloric acid (2cm³, 32%) was added and the reaction temperature was allowed to rise toroom temperature. A solution of sodium nitrite (298 mg, 4.32 mmol) inwater (5 cm³) was added drop wise with stirring and the reaction stirredat room temperature for 20 hours. The mixture was filtered and solidcollected and dried under vacuum overnight. The solid was then extractedwith methanol (15 cm³) and solvent removed under reduced pressure toyield the product as a green solid (455 mg, 52%).

δ_(H) (250 MHz, CD₃OD): 8.18 (1H, s, CH), 7.32 (2H, s, CH), 3.63 (8H, t,J₁=6 Hz, CH₂), 3.00 (4H, J₁=6 Hz, CH₂), 2.87 (4H, t, J₂=7 Hz, CH₂),2.09-2.02 (8H, m, CH₂);

_(c) (100 MHz, CD₃OD): 152.4, 151.7, 142.7, 128.0, 124.1, 113.7, 105.3,50.8, 50.2, 27.2, 20.6, 19.6, 19.5; ν_(max) (KBr)/cm⁻¹: 3042, 3028,2921, 1600, 1580, 1517, 1305, 1166, 1147; m/z (ESI): 371.3 (100%,[M−Cl]⁺).

Synthesis 22,3,6,7,12,13,16,17-Octahydro-1H,5H,11H,15H-diquinolizino[1,9-bc:1′,9′-hi]xanthyliumnitrate

2,3,6,7,12,13,16,17-Octahydro-1H,5H,11H,15H-diquinolizino[1,9-bc:1′,9′-hi]xanthyliumnitrate

7,7′-Methylenebis(2,3,6,7-tetrahydrobenzo[i,j]quinolizine-8,8′-diol)dihydrochloride (1.00 g, 2.15 mmol) was added to concentrated sulphuricacid (3 cm³) at 25° C. The resulting solution was heated to 90° C. for 2hours. The reaction was allowed to cool to room temperature before icewater (6 cm³) was added. The pH of the solution was adjusted to pH 9with sodium hydroxide (40%) whilst maintaining a temperature below 20°C. Nitric acid (0.5 cm³, 70%) was added and the reaction temperature wasallowed to rise to room temperature. The reaction was stirred at roomtemperature for 1 hour, prior to filtration. The solid was collected anddissolved in fresh water (50 cm³). Nitric acid (0.5 cm³, 70%) was addedand the reaction stirred at room temperature for 24 hours. The crudeproduct was collected by filtration and dried under vacuum overnight.The solid was re-dissolved in water (25 cm³) and nitric acid (70%) addeduntil turbidity point reached. Mixture heated to 50° C. for 1 hourbefore cooling to room temperature over 1 hour. Precipitate collectedand dried under vacuum overnight to give the product as a green solid(323 mg, 34%).

δ_(H) (250 MHz, DMSO-d₆): 8.26 (1H, s, CH), 7.35 (2H, s, CH), 3.49-3.41(8H, m, CH₂), 2.90-2.71 (8H, m, CH₂), 2.00-1.82 (8H, m, CH₂); δ_(c) (100MHz, DMSO-d₆): 152.2, 151.6, 143.1, 128.6, 124.0, 113.5, 105.3, 51.0,50.4, 27.4, 20.7, 19.8, 19.7; ν_(max) (KBr)/cm⁻¹: 2972, 2853, 1600,1514, 1436, 1361, 1336, 1299, 1200, 1164, 1093, 1030.

Synthesis 38-(Trifluoromethyl)-2,3,5,6,11,12,14,15-octahydro-1H,4H,10H,13H-diquinolizino[9,9a,1-bc;9′,9a′1′-hi]xanthyliumperchlorate

Method described in N. F. Haley, Journal of Heterocyclic Chemistry 1977,14, 683.

8-(Trifluoromethyl)-2,3,5,6,11,12,14,15-octahydro-1H,4H,10H,13H-diquinolizino[9,9a,1-bc;9′,9a′1′-hi]xanthyliumperchlorate

Trifluoroacetic acid (0.25 cm³), 8-hydroxyjulolidine (1.00 g, 5.29 mmol)and trifluoroacetic anhydride (3.94 g, 21.1 mmol) were stirred togetherin dichloromethane (8 cm³) under nitrogen at room temperature for 4days. The solvent was removed under vacuum and remaining solid added towater (100 cm³). The resulting mixture was filtered and the solid washedwith water (2×10 cm³). Perchloric acid (3 cm³) was added to the filtrateand the mixture left to stand at room temperature overnight. Theprecipitate was collected by filtration and dried. Column chromatography(1:9 methanol/dichloromethane) gave the target material as a purplesolid (67 mg, 5%).

δ_(H) (250 MHz, CDCl₃): 7.52 (2H, s, CH), 3.60 (8H, t, J₁=6 Hz, CH₂),2.97 (4H, J₁=6 Hz, CH₂), 2.88 (4H, t, J₂=7 Hz, CH₂), 2.07-2.03 (8H, m,CH₂); δ_(c) (100 MHz, CD₃OD): 152.2, 151.4, 125.9, 124.0, 123.9, 110.0,106.2, 51.0, 50.4, 27.7, 20.6, 19.7, 19.5; ν_(max) (KBr)/cm⁻¹: 2926,1598, 1500, 1317, 1297, 1265, 1150, 1109; m/z (ESI): 439.3 (100%,[M−ClO₄]⁺).

Synthesis 48-Ethyl-2,3,6,7,12,13,16,17-Octahydro-1H,5H,11H,15H-diquinolizino[1,9-bc;1′,9′-hi]xanthyliumchloride

7,7′-Propylidine-bis-(2,3,6,7-tetrahydrobenzo[i,j]quinolizine-8,8′-diol)

8-Hydroxyjulolidine (5.00 g, 26.45 mmol) was dissolved in a solution ofethanol (50 cm³) and hydrochloric acid (1.3 cm³, 32%). Propionaldehyde(767 mg, 13.23 mmol) was added to the mixture and the reaction heated to40° C. for 18 hours. An additional quantity of propionaldehyde (767 mg,13.23 mmol) was added and the reaction heated for a further 24 hours.The resulting solution was cooled and poured into water (75 cm³). Themixture was neutralised with sodium bicarbonate (saturated solution) andextracted with dichloromethane (3×40 cm³). The combined extracts weredried over sodium sulphate and the solvent removed under reducedpressure. Column chromatography (3:7 ethyl acetate/hexane) gave thetarget material as a low melting colourless solid (2.76 g, 50%).

δ_(H) (250 MHz, CDCl₃): 6.69 (2H, s, CH), 5.57 (2H, s, OH), 3.83 (1H, t,J₁=6.5 Hz, CH), 3.02-3.00 (8H, m, CH₂), 2.68-2.65 (4H, m, CH₂),2.60-2.55 (4H, m, CH₂), 2.02-1.91 (6H, m, CH₂), 0.88 (3H, t, J₂=7 Hz,CH₃); ν_(max) (KBr)/cm⁻¹: 3411, 2930, 1626, 1493, 1353, 1197.

8-Ethyl-2,3,6,7,12,13,16,17-Octahydro-1H,5H,11H,15H-diquinolizino[1,9-bc;1′,9′-hi]xanthyliumchloride

7,7′-Propylidine-bis-(2,3,6,7-tetrahydrobenzo[i,j]quinolizine-8,8′-diol)(1.00 g, 2.39 mmol) was dissolved in concentrated sulphuric acid (4 cm³)and the resulting solution heated to 90° C. for 3 hours. The reactionwas allowed to cool to room temperature prior to quenching with icewater (20 cm³). The mixture was neutralised with sodium hydroxide (40%)whilst maintaining a reaction temperature of 15° C. or below.Hydrochloric acid (2 cm³, 32%) was added and the mixture allowed to warmto room temperature. Sodium nitrite (330 mg, 4.78 mmol) in water (15cm³) was added drop wise and the reaction stirred at room temperaturefor 16 hours. The resulting precipitate was collected by filtration anddried under vacuum overnight. Column chromatography (1:9methanol/dichloromethane) gave the target material as a green solid (94mg, 9%).

δ_(H) (250 MHz, CD₃OD): 7.64 (2H, s, CH), 3.53 (8H, t, J₁=5 Hz, CH₂),3.00-2.89 (8H, m, CH₂), 2.03-2.01 (10H, m, CH₂), 1.34 (3H, t, J₂=7 Hz,CH₃); m/z (ESI): 399.3 (100%, [M−Cl]⁺).

Synthesis 5 3,6-Bis-Diethylamino Xanthylium Chloride

5,5′-Bis-diethylamino-2,2′-methandiyl-di-phenol

-   Adapted from J. Biehringer, Journal Fur Praktische Chemie 1896, 54,    235.

A suspension of 3-diethylaminophenol (200 g, 1.21 mmol) and isopropanol(600 cm³) was stirred in a 2 L jacketed reactor vessel. The jacket wasmaintained at 20° C. whilst concentrated hydrochloric acid (67 cm³, 32%)was added. The reaction was allowed to cool to 20° C. before formalin(47 cm³, 39% in water) was added drop wise over a 10 minute period. Theresulting solution was stirred at 20° C. for 3.5 hour after which thereaction was judged complete by TLC [R_(f)=0.4 (product) vs. 0.7(starting material) (3:7 Ethyl acetate/Pet. Ether 40/60)]. A solution ofammonium bicarbonate (90.0 g) in water (800 cm³) was prepared, and thenadded drop wise to the reaction over 35 minutes. The reaction wasstirred for an additional 1 hours after which the resulting solid wasfiltered and washed with water (2×200 cm³). The solid was dried at 60°C. overnight and then dissolved in isopropanol (250 cm³) under refluxfor 1 hour. The solution was cool to 5° C. over 90 minutes, and stirredat 5° C. for an additional 1 hour. The product was collected byfiltration, washed with pre-chilled isopropanol (2×100 cm³), and driedat 50° C. for 2 hours to give the target material as a light browncrystalline solid (141 g, 68%).

δ_(H) (250 MHz, CDCl₃): 7.03 (2H, d, J₁=8 Hz, CH), 6.20 (2H, dd, J₁=8Hz, J₂=3 Hz, CH), 6.14 (2H, d, J₂=3 Hz, CH), 3.71 (2H, s, CH₂), 3.22(8H, q, J₃=7 Hz, CH₂), 1.07 (12H, t, J₃=7 Hz, CH₃); δ_(c) (63 MHz,CDCl₃): 153.6, 147.7, 131.0, 116.2, 106.3, 100.9, 44.7, 29.8, 12.3;ν_(max) (KBr)/cm⁻¹: 3446, 3383, 2975, 2925, 1596, 1519, 1396, 1374,1262, 1169, 1152; m/z (ESI): 343.3 (100%, [M+H]⁺).

3,6-Bis-diethylamino xanthylium chloride

-   Adapted from J. Biehringer, Journal Fur Praktische Chemie 1896, 54,    217;-   J. Biehringer, Chemische Berichte 1894, 27, 3299; and U.S. Pat. No.    3,932,415.

5,5′-Bis-diethylamino-2,2′-methandiyl-di-phenol (2.00 g, 5.85 mmol) wasadded portion-wise to a mixture of concentrated sulphuric acid (7.2 cm³)and water (0.8 cm³). The solution was heated to 140° C. for 2 hoursunder nitrogen. The solution was allowed to cool to 5° C. prior to theaddition of ice water (10 cm³). The pH of the solution was adjusted topH 9 by the slow addition of sodium hydroxide (40%) whilst maintaining atemperature of 20° C. or below. Hydrochloric acid (3.5 cm³, 32%) wasadded and the solution allowed to warm to room temperature. Sodiumnitrite (807 mg, 11.7 mmol) dissolved in water (10 cm³) was added dropwise. Once the addition was complete the reaction was stirred at roomtemperature for 16 h. The mixture was filtered and the solid dried undervacuum for 20 hours. The solid was extracted with methanol and thesolvent removed under reduced pressure to give the product as a greensolid (1.18 g, 56%).

Scaled-Up Procedure:

5,5′-Bis-diethylamino-2,2′-methandiyl-di-phenol (10.00 g, 29.24 mmol)was added portion-wise to a mixture of concentrated sulphuric acid (28.5cm³) and water (9.5 cm³) pre-cooled to 5° C. The solution was heated to140° C. for 2 hours under nitrogen. The solution was allowed to cool to5° C. prior to the addition of ice water (50 cm³). The pH of thesolution was adjusted to pH 9 by the slow addition of sodium hydroxide(40%) whilst maintaining a temperature of 20° C. or below. Hydrochloricacid (17.5 cm³, 32%) was added and the solution allowed to warm to roomtemperature. Sodium nitrite (4.03 mg, 58.48 mmol) dissolved in water (25cm³) was added dropwise. Once the addition was complete the reaction wasstirred at room temperature for 2 h. The mixture was filtered and thesolid dried under vacuum. The solid was extracted with methanol (60 cm³)and the solvent removed under reduced pressure to give the product as agreen solid (5.78 g, 55%)_(.)

δ_(H) (250 MHz, CD₃OD): 8.51 (1H, s, CH), 7.76 (2H, d, J₁=9 Hz, CH),7.13 (2H, dd, J₁=9 Hz, J₂=3 Hz, CH), 6.88 (2H, d, J₂=3 Hz, CH), 3.68(8H, q, J₃=7 Hz, CH₂), 1.31 (12H, t, J₃=7 Hz, CH₃); δ_(c) (100 MHz,DMSO-d₆): 158.2, 156.2, 146.3, 134.2, 114.9, 114.3, 96.4, 46.0, 13.1;ν_(max) (KBr)/cm⁻¹: 2975, 2925, 1596, 1579, 1519, 1347, 1169, 1132,1076; m/z (ESI): 323.3 (100%, [M−Cl]⁺).

Synthesis 6 3,6-Bis-diethylamino xanthylium bromide 3,6-Bis-diethylaminoxanthylium bromide

Method A

5,5′-Bis-diethylamino-2,2′-methandiyl-di-phenol (5.00 g, 14.62 mmol) wasadded portion-wise to a mixture of concentrated sulphuric acid (15 cm³)and water (5 cm³). The solution was heated to 160° C. for 2 hours undernitrogen. The solution was allowed to cool to 5° C. prior to theaddition of ice water (25 cm³). The pH of the solution was adjusted topH 9 by the slow addition of sodium hydroxide (40%) whilst maintaining atemperature of 20° C. or below. Hydrobromic acid (8 cm³, 48%) was addeddrop wise and the solution allowed to warm to room temperature. Sodiumnitrite (2.02 mg, 29.24 mmol) dissolved in water (25 cm³) was added dropwise. Once the addition was complete the reaction was stirred at roomtemperature for 18 hours. The resulting precipitate was collected byfiltration and dried under vacuum to give the product as a green/brownsolid (2.51 g, 43%).

Method B

Concentrated sulphuric acid (10.8 cm³) was added to water (1.2 cm³) andthe mixture cooled to 5° C. in ice.5,5′-Bis-diethylamino-2,2′-methandiyl-di-phenol (4.00 g, 11.70 mmol) wasadded portion wise with stirring. The mixture was then heated at 110° C.for 22 hours under nitrogen. The resulting dark orange solution wascooled in ice to 5° C. before the addition of ice water (20 cm³). Themixture was neutralised by the slow addition of sodium hydroxide (40% inwater) whilst maintaining a temperature of 20° C. or below. Hydrochloricacid (12 cm³, 32%) was added drop wise and the mixture stirred at roomtemperature for 30 minutes. Iron (III) chloride (12.64 g, 46.78 mmol) inwater (12 cm³) was added and the mixture heated to 90° C. for 4 hours.The solution was allowed to cool to room temperature over 3 hours. Theresulting green precipitate was collected by filtration. The solid wasdissolved in water (60 cm³). Nitric acid (3 cm³, 70%) was added and themixture stirred at room temperature for 30 minutes. The resulting solidwas collected by filtration and dried under vacuum overnight. The solidwas dissolved in water (40 cm³) and KBr (4.00 g, 33.61 mmol) was addedand the mixture heated to 60° C. for 30 minutes. The mixture was allowedto cool to room temperature over 3 hours. The resulting solid wascollected by filtration and dried under vacuum overnight to give theproduct as a green crystalline solid (3.52 g, 74%).

Method C

Concentrated sulphuric acid (162 cm³) was added to water (18 cm³) andthe mixture cooled to 5° C. in ice.5,5′-Bis-diethylamino-2,2′-methandiyl-di-phenol (60.00 g, 0.175 mol) wasadded portion wise with stirring. The mixture was then heated at 110° C.for 22 hours under argon. The resulting dark orange solution was cooledin ice to 5° C. before the addition of ice water (300 cm³). Iron (III)chloride (94.74 g, 0.351 mol) in water (240 cm³) was added and themixture heated to 90° C. for 22 hours in air. The solution was allowedto cool to room temperature over 3 hours. The resulting greenprecipitate was collected by filtration. The solid was dissolved inwater (90 cm³). Nitric acid (50 cm³, 70%) was added and the mixturestirred at room temperature for 30 minutes. The resulting solid wascollected by filtration and dried under vacuum overnight. The solid wasdissolved in water (170 cm³) and KBr (38.00 g, 0.319 mol) was added andthe mixture heated to 60° C. for 30 minutes. The mixture was allowed tocool to room temperature over 3 hours. The resulting solid was collectedby filtration and dried under vacuum overnight to give the product as agreen crystalline solid (34.34 g, 48%).

δ_(H) (250 MHz, DMSO-d₆): 8.74 (1H, s, CH), 7.85 (2H, d, J₁=9 Hz, CH),7.19 (2H, d, J=9 Hz, CH), 6.88 (2H, s, CH), 3.65 (8H, q, J₂=6 Hz, CH),1.20 (12H, t, J₂=6 Hz, CH₃); δ_(c) (100 MHz, DMSO-d₆): 158.1, 156.2,146.2, 134.2, 114.9, 114.3, 96.4, 46.0, 19.1; ν_(max) (KBr)/cm⁻¹: 2970,1650, 1594, 1520, 1489, 1428, 1396, 1346, 1265, 1168, 1073, 1006, 968;m/z (ESI): 323.2 (100%, [M−Br]⁺).

Synthesis 7 3,6-Bis-diethylamino xanthylium iron tetrachloride3,6-Bis-diethylamino xanthylium iron tetrachloride

Method A

3,6-Bis-diethylamino xanthylium chloride (40 mg, 0.111 mmol), wasdissolved in water (5 cm³). Iron (III) chloride (30 mg, 0.111 mmol) wasadded and the solution was allowed to stand at room temperature for 2hours. Sodium chloride was added until a green precipitate was observed.This was collected by filtration and dried under vacuum overnight (53mg, 91%).

Modified Method:

3,6-Bis-diethylamino xanthylium chloride (100 mg, 0.279 mmol), wasdissolved in water (15 cm³). Iron (III) chloride (75 mg, 0.279 mmol) wasadded and the solution was allowed to stand at room temperature for 30minutes. Sodium chloride was added until a green precipitate wasobserved. This was collected by filtration and dried under vacuumovernight (141 mg, 97%).

Method B

Concentrated sulphuric acid (27 cm³) was added to water (3 cm³) and themixture cooled to 5° C. in ice.5,5′-Bis-diethylamino-2,2′-methandiyl-di-phenol (10.00 g, 29.24 mmol)was added portion wise with stirring. The mixture was then heated at140° C. for 90 minutes under nitrogen. The resulting dark orangesolution was cooled in ice to 5° C. before the addition of ice water (60cm³). The mixture was neutralised by the slow addition of sodiumhydroxide (40% in water) whilst maintaining a temperature of 20° C. orbelow. Hydrochloric acid (10 cm³, 32%) was added drop wise and themixture stirred at room temperature for 30 minutes. The mixture wasfiltered and the solid sodium sulphate washed with water (3×50 cm³).Iron (III) chloride (15.79 g, 58.47 mmol) in water (50 cm³) was added tothe filtrate and the mixture heated to 90° C. for 2 hours. The solutionwas allowed to cool to room temperature and concentrated hydrochloricacid was added slowly until precipitation of the product occurred(pH˜1). The mixture was filtered and the solid dried under vacuumovernight to give the product as a green solid (11.43 g, (5%).

δ_(H) (250 MHz, DMSO-d₆): 8.76 (1H, s, CH), 7.85 (2H, d, J₁=9 Hz, CH),7.16 (2H, dd, J₁=9 Hz, J₂=3 Hz, CH), 6.86 (2H, d, J₂=3 Hz, CH), 3.64(8H, q, J₃=7 Hz, CH₂), 1.27 (12H, t, J₃=7 Hz, CH₃); ν_(max) (KBr)/cm⁻¹:2970, 2926, 1585, 1495, 1396, 1343, 1252, 1074; m/z (ESI): 323.2 (100%,[M−FeCl₄]⁺).

Synthesis 8 3,6-Bis-diethylamino xanthene dihydrochloride

3,6-Bis-diethylamino xanthene dihydrochloride

Concentrated sulphuric acid (6 cm³) was added to water (2 cm³) and themixture cooled to 5° C. in ice.5,5′-Bis-diethylamino-2,2′-methandiyl-di-phenol (2.00 g, 5.85 mmol) wasadded portion wise with stirring. The mixture was then heated at 160° C.for 2 hours under nitrogen. The resulting dark orange solution wascooled in ice to 5° C. before the addition of ice water (10 cm³). Themixture was neutralised by the slow addition of sodium hydroxide (40% inwater) keeping the temperature below 20° C. The resulting precipitatewas collected by filtration, washed with water (2×10 cm³) and driedunder vacuum overnight. The intermediate was added to a solution ofmethanol (20 cm³) and hydrochloric acid (1.3 cm³, 32%) and stirred for 1hour until homogeneous. The solvent was removed under reduced pressureand the solid dried under vacuum overnight to give the product as apurple solid (1.03 g, 44%).

δ_(H) (250 MHz, D₂O): 7.49 (2H, d, J₁=8 Hz, CH), 7.26-7.21 (4H, m, CH),4.16 (2H, s, CH₂), 3.63 (8H, q, J₃=7 Hz, CH₂), 1.12 (12H, t, J₃=7 Hz,CH₃); ν_(max) (KBr)/cm⁻¹: 2980, 2614, 1612, 1479, 1414, 1344, 1290,1153, 1106, 1015; m/z (ESI): 325.3 (41%, [M−HCl₂]⁺).

Synthesis 9 3,6-Bis-diethylamino Xanthylium Nitrate 3,6-Bis-diethylaminoXanthylium Nitrate

Method A

Concentrated sulphuric acid (5.4 cm³) was added to water (0.6 cm³) andthe mixture cooled to 5° C. in ice.5,5′-Bis-diethylamino-2,2′-methandiyl-di-phenol (2.00 g, 5.85 mmol) wasadded portion wise with stirring. The mixture was then heated to 140° C.for 90 minutes under nitrogen. The resulting dark orange solution wascooled in ice to 5° C. before the addition of ice water (12 cm³). Themixture was neutralised by the slow addition of sodium hydroxide (40% inwater) whilst maintaining a temperature of 20° C. or below. Nitric acid(1 cm³, 70%) was added drop wise and the mixture stirred at roomtemperature for 30 minutes. The mixture was filtered and the solidsodium sulphate washed with water (3×10 cm³). Nitric acid (1 cm³, 70%)was added to the filtrate followed by the drop wise addition of sodiumnitrite (807 mg, 11.70 mmol) in water (10 cm³). The reaction was stirredat room temperature for 15 minutes, whereupon the resulting solid wascollected by filtration and dried under vacuum overnight to give theproduct as a purple/green solid (643 mg, 29%).

δ_(H) (250 MHz, DMSO-d₆): 8.55 (1H, s, CH), 7.79 (2H, d, J₁=9 Hz, CH),7.17 (2H, dd, J₁=9 Hz, J₂=2 Hz, CH), 6.93 (2H, d, J₂=2 Hz, CH), 3.69(8H, q, J₃=7 Hz, CH₂), 1.32 (12H, t, J₃=7 Hz, CH₃); δ_(C) (100 MHz,DMSO-d₆): 158.2, 156.2, 146.3, 134.2, 114.9, 96.4, 45.0, 13.1; ν_(max)(KBr)/cm⁻¹: 2978, 1596, 1522, 1493, 1387, 1347, 1264, 1168, 1074, 1007;m/z (ESI): 323.2 (100%, [M−NO₃]⁺).

3,6-Bis-diethylamino xanthylium nitrate.HNO₃

Method B

Concentrated sulphuric acid (5.4 cm³) was added to water (0.6 cm³) andthe mixture cooled to 5° C. in ice.5,5′-Bis-diethylamino-2,2′-methandiyl-di-phenol (2.00 g, 5.85 mmol) wasadded portion wise with stirring. The mixture was then heated at 140° C.for 90 minutes under nitrogen. The resulting dark orange solution wascooled in ice to 5° C. before the addition of ice water (12 cm³). Themixture was neutralised by the slow addition of sodium hydroxide (40% inwater) whilst maintaining a temperature of 20° C. or below. Nitric acid(6 cm³, 70%) was added drop wise and the mixture stirred at roomtemperature for 30 minutes until the precipitate completely dissolved.The reaction was heated to 100° C. for 24 hours and then cooled to roomtemperature. Nitric acid (0.5 cm³, 70%) was added and the resultingsolid collected by filtration.

The crude product was dissolved in fresh water (20 cm³) and nitric acid(few drops, 70%) added until product began to precipitate. The mixturewas then heated to 60° C. for 30 minutes before cooling to roomtemperature over 4 hours. The mixture was then filtered and theprecipitate dried under vacuum overnight to give the product as agreen/purple solid (467 mg, 21%).

Alternatively, the crude product was dissolved in fresh water (20 cm³)and nitric acid (few drops, 70%) added until the product precipitated.The mixture was then filtered and the precipitate dried under vacuumovernight. Material was dissolved in the minimum volume of hot IPA,cooled to 5° C. overnight, and the solid collected by filtration anddried under vacuum to give the product as a green/purple solid (401 mg,18%).

3,6-Bis-diethylamino Xanthylium Nitrate.HNO₃

Method C

3,6-Bis-diethylamino xanthylium iron tetrachloride (11.00 g, 21.11 mmol)was dissolved in water (40 cm³). Nitric acid (2 cm³, 70%) was added andthe mixture stirred at room temperature for 30 minutes. The resultingsolid was collected by filtration and dried under vacuum overnight togive the product as a purple solid (7.11 g, 54%).

δ_(H) (250 MHz, DMSO-d₆): 8.73 (1H, s, CH), 7.86 (2H, d, J=9 Hz, CH),7.21 (2H, d, J=9 Hz, CH), 6.90 (2H, s, CH), 3.72-3.55 (8H, m, CH₂), 1.21(12H, t, J=7 Hz, CH₃).

Method C described above involves the preparation of an intermediatehaving an iron tetrachloride counter ion. Nitric acid may be used toreplace that counter ion. Excessive levels of iron are generallyunacceptable in pharmaceutical products. Table 1 below shows the metallevels within a product obtained by Method C (Pyronin B NO₃ ⁻.HNO₃) incomparison with the intermediate iron tetrachloride salt (Pyronin FeCl₄⁻).

TABLE 1 Metal levels in the product of Method C Sample Metals (μg/g)Pyronin FeCl₄ ⁻ Pyronin B NO₃ ⁻•HNO₃ B 31.5 1.7 Mg 3.6 2.3* Al 12 1.8* V3.7 0.2 Cr 2.7 0.3 Mn 23.3 1.2 Fe 78982 126.8 Co 0.3 <0.04 Ni 1.8 0.5 Cu12.9 <1.01 Zn 62.6 11.5 Ga 5.0 <0.01 Sb 0.1 <0.04 Sn 10.4 0.8 Ba 1.7 1.9Pb 0.4 <0.1 Hg 54 24 Nb Present Absent Ta Present Absent Ge PresentAbsent *indicates an inhomogeneity between samples.

Synthesis 10 9-Ethyl-3,6-bis-diethylamino Xanthylium Chloride

5,5′-Bis-diethylamino-2,2′-propylidine-di-phenol

3-Diethylaminophenol (10.00 g, 60.61 mmol) was dissolved in methanol (15cm³). The solution was cooled to 5° C. before hydrochloric acid (3 cm³,32%) was added. Propionaldehyde (1.76 g, 30.30 mmol) was then added dropwise and the resulting solution was heated to 40° C. overnight. A secondportion of propionaldehyde (1.76 g, 30.30 mmol) was added and themixture heated for a further 24 hours. The mixture was poured into water(30 cm³) before the pH was adjusted to pH 8 with a saturated solution ofammonium bicarbonate. The mixture was extracted with dichloromethane(3×20 cm³). The combined organic extracts were dried (sodium sulphate),filtered and the solvent removed under reduced pressure. Columnchromatography (3:7 ethyl acetate/hexane) gave the target material as apink solid (2.11 g, 19%).

δ_(H) (250 MHz, CDCl₃): 7.05 (2H, d, J₁=8.5 Hz, CH), 6.23 (2H, dd,J₁=8.5 Hz, J₂=2.5 Hz, CH), 6.09 (2H, d, J₂=2.5 Hz, CH), 3.96 (1H, t,J₃=7 Hz, CH), 3.23 (8H, q, J₄=7 Hz, CH₂), 2.06-2.00 (2H, m, CH₂), 1.08(12H, t, J₄=7 Hz, CH₃), 0.90 (3H, t, J₃=7 Hz, CH₃); δ_(C) (62.5 MHz,CDCl₃): 153.8, 147.4, 127.5, 118.5, 105.8, 99.9, 44.3, 36.6, 26.3, 12.8,12.5; ν_(max) (KBr)/cm⁻¹: 2967, 2899, 1620, 1517, 1354, 1210, 1091,1076; m/z (ESI+): 371.3 (100%, [M+H]⁺).

9-Ethyl-3,6-Bis-diethylamino Xanthylium Chloride

-   Adapted from U.S. Pat. No. 3,932,415

5,5′-Bis-diethylamino-2,2′-propylidine-di-phenol (500 mg, 1.35 mmol) wasadded portion-wise to concentrated sulphuric acid (2 cm³). The solutionwas heated to 90° C. for 3 hours. The solution was allowed to cool toroom temperature and then poured into ice water (20 cm³). The pH of thesolution was adjusted to pH 6 by the slow addition of sodium hydroxide(40% in water). Hydrochloric acid (1 cm³, 32%) was added and thesolution allowed to warm to room temperature. Sodium nitrite (186 mg,2.70 mmol) dissolved in water (10 cm³) was added drop wise. Once theaddition was complete the reaction was stirred at room temperature for16 hours. The resulting precipitate was collected by filtration anddried under vacuum. The solid was extracted withmethanol/dichloromethane (1:20, 3×10 cm³). The solvent was removed undervacuum to give a green solid. This was then dissolved in water (10 cm³),filtered and the solid residue washed with water (2×5 cm³). The aqueoussolution was saturated with sodium chloride before it was extracted withchloroform (7×30 cm³). The combined organic extracts were dried (sodiumsulphate), filtered and the solvent removed under reduced pressure togive the product as a green solid (59 mg, 11%).

δ_(H)(250 MHz, CD₃OD): 8.11 (2H, d, J₁=8 Hz, CH), 7.17 (2H, dd, J₁=8 Hz,J₂=3 Hz, CH), 6.89 (2H, d, J₂=3 Hz, CH), 3.65 (8H, J₃=7 Hz, CH₂),3.45-3.38 (2H, m, CH₂), 1.40-1.20 (15H, m, CH₃); ν_(max) (KBr)/cm⁻¹:2972, 1592, 1469, 1398, 1343, 1248, 1185, 1132, 1073; m/z (ESI): 351.2(100%, [M−Cl]⁺).

Synthesis 11 3,6-Bis(diethylamino))thioxanthylium Iodide

4,4′-Bis(diethylamino)diphenylmethane

Acetic acid (8.05 g, 0.134 mol) was added drop wise toN,N-diethylaniline (10.0 g, 67.1 mmol). Formalin (3.00 cm³, 37% inwater) was added with stirring and the mixture heated to reflux for 90minutes. The reaction was allowed to cool, before dilution with icewater (50 cm³). The reaction was basified with saturated sodiumbicarbonate (pH 9). The resulting mixture was extracted with DCM (3×50cm³), the combined extracts were dried over sodium sulphate, filteredand the solvent removed under reduced pressure. Column chromatography(1:9 ethyl acetate/hexane, R_(f) 0.3) gave the target material as acolourless oil (10.01 g, 96%).

δ_(H) (250 MHz, CDCl₃): 7.02 (4H, d, J=8.5 Hz, CH), 6.61 (4H, d, J=8.5Hz, CH), 3.77 (2H, s, CH₂), 3.30 (8H, q, J=7 Hz, CH₂), 1.21 (12H, t, J=7Hz, CH₃); δ_(c) (63 MHz, CDCl₃): 146.1, 129.9, 129.6, 129.2, 112.2,44.5, 39.8, 12.7; ν_(max) (neat)/cm⁻¹: 2969, 2928, 1614, 1564, 1517,1465, 1354, 1264, 1195, 1151, 1075, 1012; m/z (ESI): 311.3 (100%,[M+H]⁺).

3,6-Bis(diethylamino)thioxanthylium Iodide

-   Adapted from R. H. Nealey, J. S. Driscoll, J. Hetero. Chem. 1966, 3,    228.

Sulphur (1.65 g, 51.6 mmol) was added in small portions with vigorousstirring to fuming sulphuric acid (8.00 g) over a 15 minute period. Thereaction was cooled to 5° C. and 4,4′-bis(diethylamino)diphenylmethane(2.00 g, 6.45 mmol) was added at such a rate to maintain the temperaturebelow 20° C. The reaction was then stirred at ambient temperature for 90minutes and then poured into 40 cm³ of ice. The resulting red mixturewas boiled for 1 hour and then allowed to cool to ambient temperaturebefore filtration.

Potassium iodide was added to the filtrate until a precipitate wasobserved. The mixture was cooled in ice before the green solid wascollected by filtration and dried under reduced pressure (253 mg, 8%).

δ_(H) (250 MHz, DMSO-d₆): 8.62 (1H, s, CH), 7.98 (2H, d, J=9 Hz, CH),7.36 (2H, d, J=3 Hz, CH), 7.23 (2H, dd, J=9 Hz, 3 Hz, CH), 3.68, (8H, q,J=7 Hz, CH₂), 1.23 (12H, t, J=7 Hz, CH₃); ν_(max) (KBr)/cm⁻¹: 3456,3393, 1593, 1560, 1509, 1392, 1343, 1191, 1152, 1071; m/z (ESI): 339.4(100%, [M−I]⁺).

Synthesis 12 3,6-Bis(dimethylamino)thioxanthylium Zinc Trichloride

4,4′-Bis(dimethylamino)diphenylmethane

Acetic acid (9.91 g, 0.165 mol) was added drop wise toN,N-dimethylaniline (10.00 g, 82.6 mmol). Paraformaldehyde (1.23 g, 41.3mmol) was added with stirring and the mixture heated to reflux for 90minutes. The reaction was allowed to cool, before dilution with icewater (50 cm³). The reaction was basified with 10% sodium hydroxide (pH9) and the resulting solid collected by filtration. The solid was washedwith water (2×5 cm³), and dried. Recrystallisation from ethanol gave thetarget material as a colourless solid (6.54 g, 63%).

δ_(H) (250 MHz, CDCl₃): 7.05 (4H, d, J=8.5 Hz, CH), 6.68 (4H, d, J=8.5Hz, CH), 3.80 (2H, s, CH₂), 2.62 (12H, s, CH₃); δ_(c) (62.5 MHz, CDCl₃):149.1, 130.4, 129.5, 113.1, 41.0, 39.9; ν_(max) (KBr)/cm⁻¹: 2886, 2797,1615, 1499, 1361, 1230, 1070, 828, 796;

m/z (ESI): 253.2 (100%, [M−H]⁺).

3,6-Bis(dimethylamino)thioxanthylium Zinc Trichloride

-   From R. H. Nealey, J. S. Driscoll, J. Hetero. Chem. 1966, 3, 228.

Sulphur (10.0 g, 0.33 mol) was added in small portions with vigorousstirring to fuming sulphuric acid (50 g) over a 15 minute period. Thereaction was cooled to 5° C. and 4,4′-bis(dimethylamino)diphenylmethane(10.00 g, 39.4 mmol) was added at such a rate to maintain thetemperature below 20° C. The reaction was then stirred at ambienttemperature for 90 minutes and then poured into 250 cm³ of ice. Theresulting red mixture was boiled for 1 hour and then allowed to cool toambient temperature before filtration. A 40% aqueous solution of zincchloride was added to the filtrate until a green colour was observed.The mixture was cooled in an ice bath and the solid collected byfiltration. The solid was dried overnight under reduced pressure to givethe target material as a green solid (1.81 g, 10%).

δ_(H) (250 MHz, DMSO-d₆): 8.68 (1H, s, CH), 8.01 (2H, d, J=9 Hz, CH),7.37 (2H, d, J=3 Hz, CH), 7.25 (2H, dd, J=9 Hz, 3 Hz, CH), 3.28 (12H, s,CH₃); δ_(c) (62.5 MHz, DMSO-d₆): 154.5, 149.3, 143.6, 138.1, 119.0,116.2, 106.4, 41.0; ν_(max) (KBr)/cm⁻¹: 3755, 3381, 1614, 1599, 1527,1395, 1179, 1073; m/z (ESI): 283.2 (100%, [M−ZnCl₃]⁺).

Synthesis 13 3,6-Bis(dimethylamino)-1,9-dimethylthioxanthylium ZincTrichloride

4,4′-Bis(dimethylamino)-2,2-dimethyldiphenylmethane

Hydrochloric acid (1.5 cm³, 10 M) was added drop wise to a solution of3-N,N-trimethylaniline (5.00 g, 37.0 mmol) in methanol (10 cm³) cooledto 5° C. Formalin (1.50 cm³, 40% in water) was added and the reactionallowed to stand at 6° C. for 48 hours. The resulting colourlesscrystals were collected by filtration, washed with cold methanol (5 cm³)and dried under reduced pressure (4.13 g, 79%).

δ_(H) (250 MHz, CDCl₃): 6.77 (2H, d, J=8.5 Hz, CH), 6.64 (2H, d, J=3 Hz,CH), 6.54 (2H, dd, J=8.5, 3 Hz, CH), 3.75 (2H, s, CH₂), 2.91 (12H, s,CH₃), 2.24 (6H, s CH₃);

δ_(c) (62.5 MHz, CDCl₃): 149.2, 137.1, 129.9, 127.7, 114.9, 110.7, 41.0,34.9, 20.2; ν_(max) (KBr)/cm⁻¹: 3341, 3328, 1613, 1507, 1344, 1330,1226, 1059, 1010, 841, 799; m/z (ESI): 283.2 (100%, [M+H]⁺).

3,6-Bis(dimethylamino)-1,9-dimethylthioxanthylium zinc trichloride

-   Adapted from R. H. Nealey, J. S. Driscoll, J. Hetero. Chem. 1966, 3,    228.

Sulphur (907 mg, 28.4 mmol) was added in small portions with vigorousstirring to fuming sulphuric acid (5.0 cm³) over a 15 minute period. Thereaction was cooled to 5° C. and4,4′-bis(dimethylamino)-2,2-dimethyldiphenylmethane (1.00 g, 3.55 mmol)was added at such a rate to maintain the temperature below 20° C. Thereaction was then stirred at ambient temperature for 90 minutes and thenpoured into 30 cm³ of ice. The resulting red mixture was boiled for 1hour and then allowed to cool to ambient temperature before filtration.A 40% aqueous solution of zinc chloride was added to the filtrate untila green colour was observed. The mixture was cooled in an ice bath andthe solid collected by filtration. This precipitation was repeated andthe resulting solid was dried overnight under reduced pressure to givethe target material as a green solid (98 mg, 6%).

δ_(H) (250 MHz, DMSO-d₆): 8.58 (1H, s, CH), 7.19 (2H, s, CH), 7.17 (2H,s, CH), 3.24 (12H, s, CH₃), 2.84 (6H, s, CH₃); δ_(c) (62.5 MHz,DMSO-d₆): 154.1, 145.7, 144.2, 141.6, 118.1, 116.7, 104.6, 40.9, 20.2;m/z (ESI): 311.2 (100%, [M−ZnCl₃]⁺).

Synthesis 14 3,7-Bis(dimethylamino)phenazinium chloride

N,N-dimethyl-1,3-phenylenediamine

N,N-dimethyl-3-nitroaniline (3.00 g, 18.1 mmol) was dissolved in ethanol(40 cm³). Tin dichloride (16.3 g, 72.0 mmol) was added and the reactionheated under reflux for 16 h. The reaction mixture was allowed to coolbefore the bulk of the solvent was removed under reduced pressure. Theremaining residue was poured in to water (100 cm³), and basified withsodium hydroxide (3M). The mixture was extracted with chloroform (3×30cm³). The combined extracts were dried over sodium sulphate, filteredand the solvent removed under reduced pressure to give the product as abrown oil (2.01 g, 82%)_(.)

δ_(H) (250 MHz, CDCl₃): 7.02 (1H, t, J=8 Hz, CH), 6.23 (1H, dd, J=6 Hz,J=3 Hz, CH), 6.12 (1H, t, J=3 Hz, CH), 6.09 (1H, s, CH), 2.94 (6H, s,CH₃); δ_(c) (62.5 MHz, CDCl₃): 151.8, 147.4, 129.9, 104.3, 103.8, 99.6,40.7; ν_(max) (neat)/cm⁻¹: 2879, 2800, 1611, 1504, 1443, 1354, 1260,1174, 994.

N-[3-(dimethylamino)phenyl]methanesulphonamide

Methanesulphonyl chloride (838 mg, 7.35 mmol) was added slowly to acooled solution (5° C.) of N,N-dimethyl-1,3-phenylenediamine (1.00 g,7.35 mmol) and sodium hydroxide (5M, 1.5 cm³) in water (10 cm³). Thereaction was allowed to warm to room temperature overnight. The mixturewas extracted with chloroform (3×15 cm³). The combined extracts weredried over sodium sulphate, filtered and the solvent removed underreduced pressure. Column chromatography (1:20 methanol/dichloromethane)gave the target material as a brown oil (1.24 g, 79%).

δ_(H) (250 MHz, CDCl₃): 7.20 (1H, t, J=8 Hz, CH), 6.55-6.47 (3H, m, CH),3.00 (3H, s, CH₃), 2.95 (6H, s, CH₃); δ_(c) (62.5 MHz, CDCl₃): 151.6,137.8, 130.1, 109.5, 108.5, 104.6, 40.8, 38.7; ν_(max) (neat)/cm⁻¹:2929, 2806, 1607, 1511, 1394, 1321, 1231, 1148, 1004, 940;

3,7-Bis(dimethylamino)phenazinium chloride

-   Adapted from D. F. Gloster, L. Cincotta, J. W. Foley, J.    Heterocyclic Chem. 1999, 36, 25.

N,N-dimethyl-1,4-phenylenediamine hydrochloride (402 mg, 2.34 mmol) inwater (40 cm³) was added slowly toN-[3-(dimethylamino)phenyl]methanesulphonamide (500 mg, 2.34 mmol) inmethanol (20 cm³). A saturated solution of potassium dichromate (1 cm³)was added and the mixture refluxed for 15 min. The mixture was cooledand diluted with water (80 cm³), acidified with hydrochloric acid (1M)and then extracted with chloroform (3×30 cm³). The combined extractswere dried over sodium sulphate, filtered and the solvent removed underreduced pressure. Column chromatography (1:9 methanol/dichloromethane)gave the target material as a green solid (153 mg, 22%).

δ_(H) (250 MHz, CDCl₃): 7.90 (2H, d, J=10 Hz, CH), 7.35 (2H, dd J=10 Hz,J=3 Hz, CH), 7.02 (2H, d, J=3 Hz, CH), 3.18 (12H, s, CH₃); ν_(max)(KBr)/cm⁻¹: 2854, 1596, 1506, 1475, 1428, 1338, 1167, 1142, 807.

Synthesis 15 3,7-Bis(dimethylamino)oxazinium chloride

3,7-Bis(dimethylamino)oxazinium chloride

-   Adapted from A. Kanitz, H, Hartmann, Eur, J, Org, Chem. 1999, 923.

3-Dimethylaminophenol (910 mg, 6.67 mmol), N,N-dimethyl-4-nitrosoaniline(1.00 g, 6.67 mmol) and perchloric acid (1 cm³) were heated together inethanol (20 cm³) for 5 min. The reaction was left to stand at roomtemperature overnight. The resulting solid was collected by filtrationand washed with EtOAc (2×5 cm³). Column chromatography (1:9methanol/dichloromethane) gave the product as a green/blue solid (13 mg,1%).

δ_(H) (250 MHz, CD₃OD): 7.80 (2H, d, J=10 Hz , CH), 7.41 (2H, dd, J=10Hz, 3 Hz, CH), 6.96 (2H, d, J=3 Hz, CH), 3.31 (12H, s, CH₃); ν_(max)(KBr)/cm⁻¹: 1607, 1526, 1490, 1397, 1346, 1179, 1094, 772.

Synthesis 16 3,6-Bis-(dimethylamino)xanthylium nitrate

5,5′-Bis-(dimethylamino)-2,2′-methandiyl-di-phenol

3-(Dimethylamino)phenol (3.00 g, 21.87 mmol) was added to MeOH (30 cm³).The mixture was cooled to 6° C. in ice before HCl (1.24 cm³, 10.93 mmol,32%) was added. Formalin (842 μl, 10.93 mmol, 39%) was added to thereaction mixture. The reaction was stirred at ˜6° C. for 22 h afterwhich TLC analysis [2:3 EtOAc/Hexane (R_(f)0.3)] showed the reaction tobe complete. The reaction mixture was poured into H₂O (40 cm³) and theresulting mixture neutralised by the addition of an aqueous solution ofNaHCO₃ (sat.). The mixture was extracted with DCM (3×30 cm³) and thecombined extracts dried (Na₂SO₄). The solvent was removed under reducedpressure to yield a purple solid. Column chromatography (2:3EtOAc/Hexane) gave the product as a purple solid (1.74 g, 56%).

δ_(H) (250 MHz, CDCl₃): 7.05 (2H, d, J=8 Hz, 2ArH), 6.27 (2H, d, J=8 Hz,2ArH), 6.13 (2H, s, 2ArH), 3.73 (2H, s, CH₂), 2.75 (12H, s, 4CH₃); δ_(c)(62.5 MHz, CDCl₃): 153.5, 150.9, 130.8, 116.5, 106.5, 101.2, 41.0, 29.8;ν_(max) (KBr)/cm⁻¹: 3366, 2975, 2929, 1626, 1561, 1519, 1438, 1362,1241, 1142, 1112, 980; m/z (ESI): 287.17 (100%, [M+H]⁺).

3,6-Bis-(dimethylamino)xanthylium nitrate

H₂SO₄ (1.6 cm³, 98%) was added to H₂O (160 EN) and cooled to 6° C. inice. 5,5′-Bis-(dimethylamino)-2,2′-methandiyl-di-phenol (440 mg, 1.40mmol) was added and the mixture heated to 90° C. under N₂ for 17 h. Theresulting solution was cooled to 6° C. in ice and H₂O (4 cm³) added. Themixture was neutralised by the addition of NaOH (40%) whilst maintaininga reaction temperature of less than 15° C. HCl (800 μl, 32%) was addedand the reaction stirred at 20° C. for 30 min. under N₂. FeCl₃.6H₂O (755mg, 2.80 mmol) in H₂O (4 cm³) was added and the mixture heated to 90° C.for 2 h in air. The reaction was allowed to cool to room temperatureovernight whereupon a green oil precipitated. The bulk pinkish solutionwas decanted and the remaining oil taken up in MeOH (20 cm³). Themixture was filtered and the solvent removed under vacuum. The oil wasdissolved in H₂O (8 cm³) and HNO₃ (few drops, 70%) was added slowlyuntil a purple/green solid precipitated. This was collected byfiltration and dried under vacuum overnight to give the product as agreen solid (190 mg, 41%).

δ_(H) (250 MHz, DMSO-d₆): 8.72, (1H, s ArH), 7.83 (2H, d, J=7 Hz, 2ArH),7.17 (2H, d, J=7 Hz, 2ArH), 6.83 (2H, s, 2ArH), 3.27 (12H, s, 4CH₃);δ_(c) (62.5 MHz, CDCl₃): 157.8, 157.7, 145.9, 132.8, 114.1, 114.0, 95.9,39.6; ν_(max) (KBr)/cm⁻¹: 2921, 1653, 1604, 1528, 1497, 1384, 1168, 918;m/z (ESI): 267.15 (100%, [M−NO₃]⁺).

Synthesis 17 3,6-Bis-diethylamino-9-(4-diethylanilino)xanthylium nitrate

5,5=Bis-dimethylamino-2,2′44-diethylaminobenzilidine)-di-phenol

3-Dimethylamino-phenol (5.00 g, 30.30 mmol) was added to MeOH (20 cm³).HCl (1.73 cm³, 15.15 mmol, 32%) was then added to the mixture.4-diethylamino-benzaldehyde (2.68 g, 15.15 mmol) was added to thereaction mixture. The reaction was stirred at room temperature for 20 hafter which TLC analysis [2:3 EtOAc/Hexane (Rf: 0.25)] showed thereaction to be complete. The reaction mixture was poured into H2O (40cm³) and the resulting mixture neutralised by the addition of an aqueoussolution of NaHCO3 (sat.). The mixture was extracted with DCM (3×40 cm3)and the combined extracts dried (Na2SO4). The solvent was removed underreduced pressure to yield a red oil. Column chromatography (2:3EtOAc/Hexane) gave the product as a red solid (4.15 g, 57%).

δ_(H) (250 MHz, CDCl₃): 7.03 (2H, d, J=8 Hz, 2ArH), 6.71 (2H, d, J=8 Hz,2ArH), 6.57 (2H, d, J=8 Hz, 2ArH), 6.23-6.18 (2H, m, 2ArH), 6.21 (2H, s,2ArH), 5.33 (1H, s, CH), 4.98 (2H, bs, OH), 3.33-3.24 (12H, m, 6CH₂),1.12 (18H, t, J=7 Hz, 6CH₃); δ_(c) (100 MHz, CDCl₃): 155.1, 148.3,146.7, 130.5, 130.2, 130.1, 128.1, 116.1, 112.1, 104.7, 100.0, 44.3,44.0, 12.7, 12.6; ν_(max) (KBr)/cm⁻¹: 2969, 2929, 2869, 1618, 1516,1465, 1399, 1374, 1355, 1266, 1228, 1199, 1094; m/z (ESI): 490.34 (100%,[M+H]⁺).

3,6-Bis-diethylamino-9-(4-diethylanilino)xanthylium nitrate

H₂SO₄ (5.4 cm³, 98%) was added to H₂O (600 μl) and cooled to 5° C. inice. 5,5′-Bis-dimethylamino-2,2′-(4-diethylaminobenzilidine)-di-phenol(2.00 g, 4.19 mmol) was added and the mixture heated to 150° C. under N₂for 3 h. The resulting solution was cooled to 5° C. in ice and H₂O (20cm³) added. The mixture was neutralised by the addition of NaOH (40%)whilst maintaining a reaction temperature of less than 20° C. HCl (4cm³, 32%) was added and the reaction stirred at 5° C. for 2 h under N₂.FeCl₃.6H₂O (2.26 g, 8.39 mmol) in H₂O (20 cm³) was added and the mixtureheated to 90° C. for 2 h in air. The reaction was allowed to cool toroom temperature overnight. NaCl was added until a precipitate appeared.The solid was collected by filtration and dried under vacuum. The solidwas extracted with MeOH (40 cm³). The solvent was removed under vacuumto yield a green solid. This material was dissolved in H₂O (12 cm³) andHNO₃ (1 cm³, 70%) was added slowly until a purple/green solidprecipitated. After 10 min the solid was collected by filtration anddried under vacuum to give the product as a green solid (1.11 g, 50%).

δ_(H) (250 MHz, CD₃OD): 7.50-7.40 (4H, m, 4ArH), 7.20-7.03 (4H, m,4ArH), 6.93 (2H, s, 2ArH), 3.72-3.45 (12H, m, 6CH₂), 1.30-1.15 (18H, t,J=7 Hz, 6CH₃); δ_(c) (100 MHz, CDCl₃): 159.6, 157.3, 156.5, 141.3,133.4, 123.5, 115.9, 97.7, 54.5, 47.1, 13.0, 11.2; ν_(max) (KBr)/cm⁻¹:1646, 1594, 1473, 1419, 1384, 1349, 1186, 1073; m/z (ESI): 470.32 (100%,[M−NO₃]⁺).

Synthesis 18 3,6-Bis-diethylamino-9-(4-nitrophenyl)xanthylium nitrate

5,5′-Bis-dimethylamino-2,2′-(4-nitrobenzilidine)-di-phenol

3-Dimethylamino-phenol (3.00 g, 18.18 mmol) was added to MeOH (30 cm³).HCl (1.04 cm³, 9.09 mmol, 32%) was then added to the mixture.4-nitro-benzaldehyde (1.37 g, 9.09 mmol) was added to the reactionmixture. The reaction was heated to 40° C. for 18 h and the 50° C. for24 h after which TLC analysis [1:1 EtOAc/Hexane (R_(f) 0.3)] showed thereaction to be almost complete. The reaction mixture was poured into H₂O(40 cm³) and the pH of resulting mixture basified by the addition of anaqueous solution of NaHCO₃ (sat.). The mixture was extracted with DCM(3×30 cm³) and the combined extracts dried (Na₂SO₄). The solvent wasremoved under reduced pressure to yield a red oil. Column chromatography(1:1 EtOAc/Hexane) gave the product as an orange red solid (2.84 g,69%).

δ_(H) (250 MHz, CDCl₃): 8.11 (2H, d, J=8 Hz, 2ArH), 7.34 (2H, d, J=8 Hz,2ArH), 6.65 (2H, d, J=8 Hz, 2ArH), 6.20-6.15 (4H, m, 4ArH), 5.71 (1H, s,CH), 3.27 (8H, q, J=7 Hz, 4CH₂), 1.11 (12H, t, J=7 Hz, 4CH₃); δ_(c) (100MHz, CDCl₃): 154.5, 151.8, 148.4, 146.2, 130.6, 130.0, 123.4, 115.1,104.9, 99.8, 44.4, 43.9, 12.6; ν_(max) (KBr)/cm⁻¹: 2971, 1618, 1559,1540, 1522, 1457, 1343, 1375, 1228, 1094; m/z (ESI): 464.25 (100%,[M+H]⁺).

3,6-Bis-diethylamino-9-(4-nitrophenyl)xanthylium nitrate

H₂SO₄ (1.2 cm³, 98%) was added to H₂O (120 μl) and cooled to 5° C. inice. 5,5′-Bis-dimethylamino-2,2′-(4-nitrobenzilidine)-di-phenol (400 mg,0.863 mmol) was added and the mixture heated to 70° C. under N₂ for 20 hand then at 90° C. for 29 h. The resulting solution was cooled to 6° C.in ice and H₂O (4 cm³) added. The mixture was neutralised by theaddition of NaOH (20%) whilst maintaining a reaction temperature of lessthan 16° C. HCl (1.2 cm³, 32%) was added and the reaction stirred at 19°C. for 30 min under N₂. FeCl₃.6H₂O (467 mg, 1.73 mmol) in H₂O (4 cm³)was added and the mixture heated to 88° C. for 3 h in air. The reactionwas allowed to cool to 20° C. overnight. The resulting green precipitatewas collected by filtration and dried under vacuum overnight. Thismaterial was dissolved in H₂O (4 cm³) and HNO₃ (few drops, 70%) wasadded slowly until a purple/green solid precipitated. After 10 min thesolid was collected by filtration and dried under vacuum. Columnchromatography (1:9 MeOH/DCM) gave the product as a green solid (243 mg,56%).

δ_(H) (250 MHz, CD₃OD): 8.53 (2H, d, J=7 Hz, 2ArH), 7.76 (2H, d, J=7 Hz,2ArH), 7.30 (2H, d, J=7 Hz, 2ArH), 7.10 (2H, d, J=7 Hz, 2ArH), 7.02 (2H,s, 2ArH), 3.83-3.57 (8H, m, 4CH₂), 1.44-1.18 (12H, m, 4CH₃); δ_(c) (100MHz, CD₃OD): 158.0, 155.9, 154.5, 148.9, 138.7, 131.1, 130.8, 123.6,114.4, 112.8, 96.2, 45.5, 11.4; ν_(max) (KBr)/cm⁻¹: 2977, 1647, 1593,1467, 1384, 1347, 1184, 1074; m/z (ESI): 444.23 (100%, [M−NO₃]⁺).

Synthesis 191,1,7,7,11,11,17,17-Octamethyl-2,3,6,7,12,13,16,17-octahydro-1H,5H,11H,15H-diquinolizino[1,9-bc;1′,9′-hi]xanthyliumnitrate

3-Methoxy-N,N-Bis(3-methylbut-2-ene)aniline

-   Uddin, M. J., Marnett L., J., Organic Letters, 10, 2008, 4799.

To a solution of anisidine (5.00 g, 40 65 mmol) in CH₃CN (20 cm³), K₂CO₃(11.22 g, 80.13 mmol) and 1-chloror-3-methylbut-2-ene (8.49 g, 80.13mmol) were added. Molecular sieves (4 Å, 10 g) were added and thereaction stirred at room temperature for 48 h. The resulting mixture wasfiltered and the solid washed with CH₃CN (2×15 cm³). The solvent wasremoved from the filtrate under reduced pressure. Column chromatography[1:1 40:60 petrol/DCM (R_(f) 0.4)] gave the product as a colourless oil(8.54 g, 81%).

δ_(H) (250 MHz, CDCl₃): 7.14-7.07 (1H, m, ArH), 6.32 (1H, d, J=8 Hz,ArH), 6.30-6.25 (2H, m, 2ArH), 5.23-5.19 (2H, m, 2CH), 3.84 (4H, d, J=6Hz, 2CH₂), 3.77 (3H, s, OCH₃), 1.72 (6H, s, 2CH₃), 1.70 (6H, s, 2CH₃);δ_(c) (62.5 MHz, CDCl₃): 160.8, 150.5, 134.1, 129.8, 121.8, 105.9,101.0, 99.1, 55.1, 48.4, 25.8, 18.0; ν_(max) (neat)/cm⁻¹: 2967, 2927,1671, 1610, 1498, 1452, 1376, 1327, 1263, 1214, 1164, 1060, 1043, 986,941; m/z (ESI): 260.20 (100%, [M+H]⁺).

3-Methoxy-N,N-Bis(3-methylbut-2-ene)aniline hydrochloride

-   Based on Uddin, M. J., Marnett L., J., Organic Letters, 10, 2008,    4799.

3-Methoxy-N,N-Bis(3-methylbut-2-ene)aniline (7.50 g, 28.96 mmol) wasdissolved in EtOH (20 cm³). HCl (9.65 cm³, 32%) was added and thereaction mixture stirred at room temperature for 1 h. The solvent wasremoved under vacuum overnight to yield the product as a colourlesssticky solid (8.33 g, 97%).

δ_(H) (250 MHz, DMSO-d₆): 7.55-7.35 (3H, m, 3ArH), 7.04-6.95 (1H, m,ArH), 5.30-5.02 (2H, m, 2CH), 4.30-4.01 (4H, m, 2CH₂), 3.78 (3H, s,OCH₃), 1.56 (6H, s, 2CH₃), 1.52 (6H, s, 2CH₃);

1,1,7,7-tetramethyl-8-hydroxyjulolidine

3-Methoxy-N,N-Bis(3-methylbut-2-ene)aniline hydrochloride (7.00 g, 17.68mmol) was added to methanesulphonic acid (70 cm³). The resultingsolution was heated to 95° C. for 24 h. It was then cooled to roomtemperature and ice water (140 cm³) added. The mixture was neutralisedby the addition of NH₄OH (sat.) and then extracted with CHCl₃ (3×60cm³). The extracts were dried (Na₂SO₄) and the solvent removed underreduced pressure. Column chromatography [3:2 40:60 petrol/DCM (R_(f)0.25)] gave the product as a pink solid (3.04 g, 52%).

δ_(H) (250 MHz, CDCl₃): 6.89 (1H, d, J=8 Hz, ArH), 6.00 (1H, d, J=8 Hz,ArH), 4.50 (1H, s, OH), 3.09-2.99 (4H, m, 2CH₂), 1.80-1.72 (4H, m,2CH₂), 1.42 (6H, s, 2CH₃), 1.24 (6H, s, 2CH₃); δ_(c) (62.5 MHz, CDCl₃):153.2, 143.6, 125.0, 124.3, 116.8, 105.3, 47.8, 47.4, 40.6, 37.4, 32.4,32.3, 29.2; ν_(max) (KBr)/cm⁻¹: 2953, 2928, 2859, 2826, 1586, 1424,1385, 1272, 1165, 1133, 1102, 952, 800; m/z (ESI): 246.19 (100%,[M+H]⁺).

7,7-Methylene-bis(1,1,7,7-tetramethyl-8-hydroxyjulolidine)dihydrochloride

1,1,7,7-tetramethyl-8-hydroxyjulolidine (800 mg, 3.27 mmol) was added toMeOH (10 cm³). HCl (186 μl, 1.63 mmol, 32%) was then added to themixture. Formalin (122 μl, 1.63 mmol, 39%) was added to the reactionmixture. The reaction was heated to 60° C. for 16 h and the after whichTLC analysis [3:7 EtOAc/Hexane (R_(f) 0.6)] showed the reaction to becomplete. The reaction volume was reduced by half under reduced pressureand the remainder cooled to −6° C. overnight. The resulting precipitatewas collected by filtration and dried under vacuum to give the productas a green solid (494 mg, 60%).

δ_(H) (250 MHz, DMSO-d₆): 8.95 (2H, bs, 20H), 7.08 (2H, s, 2ArH), 3.90(2H, s, CH₂), 3.39-3.25 (4H, m, 2CH₂), 2.19-1.86 (4H, m, 2CH₂), 1.41(6H, s, 2CH₃), 1.17 (6H, s, 2CH₃); ν_(max) (KBr)/cm⁻¹: 3390, 2960, 2928,2619, 2531, 1472, 1428, 1386, 1361, 1265, 1177; m/z (ESI): 503.36 (100%,[M−HCl₂]⁺).

1,1,7,7,11,11,17,17-Octamethyl-2,3,6,7,12,13,16,17-octahydro-1H,5H,11H,15H-diquinolizino[1,9-bc;1′,9′-hi]xanthyliumnitrate

H₂SO₄ (600 μl, 98%) was added to H₂O (60 μl) and cooled to 5° C. in ice.7,7-Methylene-bis(1,1,7,7-tetramethyl-8-hydroxyjulolidine)dihydrochloride (200 mg, 0.348 mmol) was added and the mixture heated to50° C. under N₂ for 4 h and then 65° C. for 2 h. The resulting solutionwas cooled to 6° C. in ice and H₂O (2 cm³) added. The mixture wasneutralised by the addition of NaOH (20%) whilst maintaining a reactiontemperature of less than 18° C. HCl (400 μl, 32%) was added and thereaction stirred at 20° C. for 30 min under N₂. FeCl₃.6H₂O (188 mg,0.696 mmol) in H₂O (1 cm³) was added and the mixture heated to 89° C.for 3 h in air. The reaction was allowed to cool to room temperatureovernight. The resulting solid was collected by filtration and driedunder vacuum overnight. This material was dissolved in H₂O (20 cm³) andHNO₃ (70%) was added slowly until a green solid precipitated. After 10min the solid was collected by filtration and dried under vacuum to givethe product as a green solid (126 mg, 66%).

δ_(H) (250 MHz, CD₃OD): 8.29 (1H, s, ArH), 7.58 (2H, d, J=8 Hz, 2ArH),3.66 (4H, t, J=6 Hz, 2CH₂), 3.57 (4H, t, J=5 Hz, 2CH₂), 1.87 (4H, t, J=5Hz, 2CH₂), 1.82 (4H, t, J=6 Hz, 2CH₂), 1.71 (13H, s, 4CH₂), 1.37 (12H,s, 4CH₃); δ_(c) (100 MHz, CD₃OD): 154.3, 151.8, 144.3, 132.9, 126.7,114.3, 114.2, 38.8, 33.8, 31.9, 31.6, 27.8, 27.6; ν_(max) (KBr)/cm⁻¹:2957, 1596, 1507, 1384, 1309, 1202, 1038; m/z (ESI): 483.34 (100%,[M−NO₃]⁺).

Synthesis 20 3,6-Bis-morpholino-xanthylium nitrate

N-(3-Hydroxyphenyl)morpholine

Pd(OAc)₂ (78 mg, 0.347 mmol) was added to morpholine (1.81 g, 20.81mmol) and 3-bromophenol (3.00 g, 17.34 mmol) under N₂.2,8,9-triisobutyl-2,5,8,9-tetraaza-1-phosphabicyclo[3,3,3]undecane (238mg, 0.694 mmol), LiHMDS (39.88 cm³, 1 M in THF) and dry toluene (80 cm³)were added sequentially. The mixture was heated to 80° C. for 18 h,before being cooled to room temperature. The solvent was removed undervacuum and the residue extracted with hot EtOAc/DCM (1:1, 200 cm³). Themixture was filtered and the solvent removed. Column chromatography [1:1EtOAc/DCM (R_(f) 0.25)] gave the product as an off-white solid (2.38 g,77%).

δ_(H) (250 MHz, CDCl₃): 7.14-7.08 (1H, m, ArH), 6.48 (1H, d, J=8 Hz,ArH), 6.36-6.32 (2H, m, 2ArH), 5.82 (1H, bs, OH), 3.85 (4H, t, J=5 Hz,2CH₂), 3.11 (4H, t, J=5 Hz, 2CH₂); δ_(c) (62.5 MHz, CDCl₃): 156.9,152.6, 130.2, 108.2, 107.6, 103.2, 66.8, 49.4; ν_(max) (KBr)/cm⁻¹: 3242,2974, 2816, 1610, 1582, 1491, 1448, 1267, 1191, 1104, 1064, 975, 773;m/z (ESI): 180.10 (100%, [M+H]⁺).

5,5=Bis-morpholino-2,2=methandiyl-di-phenol

N-(3-Hydroxyphenyl)morpholine (2.00 g, 11.17 mmol) was added to MeOH (25cm³). The mixture was cooled to 5° C. in ice before HCl (637 μl, 5.89mmol, 32%) was added. Formalin (419 μl, 5.89 mmol, 39%) was added to thereaction mixture. The reaction was stirred at 5° C. for 18 h, and thenat room temperature for 24 h. The reaction mixture was poured into H₂O(40 cm³) and the resulting mixture neutralised by the addition of anaqueous solution of NaHCO₃ (sat.). The mixture was extracted with DCM(3×30 cm³) and the combined extracts dried (Na₂SO₄). The solvent wasremoved under reduced pressure. Column chromatography [4:1 EtOAc/Hexane(R_(f) 0.3)] gave the product as a purple solid (684 mg, 33%).

δ_(H) (250 MHz, DMSO-d₆): 9.08 (2H, s, OH), 6.76 (2H, d, J=8 Hz, 2ArH),6.35 (2H, s, 2ArH), 6.29 (2H, d, J=8 Hz, 2ArH), 3.72-3.68 (8H, m, 4CH₂),3.59 (2H, s, CH₂), 2.98-2.94 (8H, m, 4CH₂); δ_(c) (62.5 MHz, DMSO-d₆):155.3, 150.5, 130.4, 118.7, 106.5, 102.2, 66.2, 49.0, 28.0; ν_(max)(KBr)/cm⁻¹: 3246, 2965, 2825, 1618, 1584, 1527, 1451, 1261, 1191, 1112,981, 882; m/z (ESI): 371.19 (100%, [M+H]⁺).

3,6-Bis-(morpholino)xanthylium nitrate

H₂SO₄ (900 μl, 98%) was added to H₂O (100 μl) and cooled to roomtemperature. 5,5′-bis-morpholino-2,2′-methandiyl-di-phenol (300 mg,0.811 mmol) was added and the mixture heated to 140° C. under N₂ for 3h. The resulting solution was cooled to room temperature and H₂O (2 cm³)added. The mixture was neutralised by the addition of NaOH (40%) whilstmaintaining a reaction temperature of less than 15° C. HCl (600 μl, 32%)was added and the reaction stirred at room temperature for 30 min. underN₂. FeCl₃.6H₂O (438 mg, 1.62 mmol) in H₂O (2 cm³) was added and themixture heated to 90° C. for 2 h in air. The reaction was allowed tocool to room temperature. The resulting solid was collected byfiltration and dried under vacuum. This material was dissolved in H₂O(10 cm³) and HNO₃ (300 μl, 70%) was added slowly until a green solidprecipitated. After 10 min the solid was collected by filtration anddried under vacuum to give the product as a green solid (198 mg, 67%).

δ_(H) (250 MHz, CD₃OD): 8.70 (1H, s, ArH), 7.87 (2H, d, J=7 Hz, 2ArH),7.37 (2H, d, J=7 Hz, 2ArH), 7.15 (2H, s, 2ArH), 3.86-3.85 (8H, m, 4CH₂),3.79-3.67 (8H, m, 4CH₂); δ_(c) (100 MHz, CD₃OD): 158.4, 157.9, 146.5,133.3, 115.2, 114.6, 96.9, 66.0, 46.9; ν_(max) (KBr)/cm⁻¹: 2865, 1598,1489, 1384, 1244, 1170, 1109, 1034, 903; m/z (ESI): 351.17 (100%,[M−NO₃]⁺).

Synthesis 21 3,6-Bis-piperidino-xanthylium nitrate

N-(3-Hydroxyphenyl)piperidine

Pd(OAc)₂ (129 mg, 0.578 mmol) was added to piperidine (2.95 g, 34.68mmol) and 3-bromophenol (5.00 g, 28.90 mmol) under N₂.2,8,9-triisobutyl-2,5,8,9-tetraaza-1-phosphabicyclo[3,3,3]undecane (397mg, 1.16 mmol), LiHMDS (66.50 cm³, 1 M in THF) and dry toluene (110 cm³)were added sequentially. The mixture was heated to 80° C. for 18 h,before being cooled to room temperature. H₂O (50 cm³) was added and thelayers separated. The aqueous layer was extracted with toluene (3×30cm³). The combined organics were dried (Na₂SO₄) and the solvent removedunder reduced pressure. Column chromatography [3:7 EtOAc/Hexane (R_(f)0.4)] gave the product as an off-white solid (2.56 g, 50%).

δ_(H) (250 MHz, CDCl₃): 7.11-7.04 (1H, m, ArH), 6.52 (1H, d, J=8 Hz,ArH), 6.35 (1H, s, ArH), 6.29 (1H, d, J=8 Hz, ArH), 5.84 (1H, bs, OH),3.08 (4H, t, J=5 Hz, 2CH₂), 1.75-1.62 (4H, m, 2CH₂), 1.60-1.50 (2H, m,CH₂); δ_(c) (62.5 MHz, CDCl₃): 156.7, 153.4, 130.0, 109.3, 107.4, 104.6,51.0, 25.5, 24.2; ν_(max) (KBr)/cm⁻¹: 3064, 2959, 2937, 2921, 2856,1597, 1503, 1454, 1276, 1201, 1133, 1104, 971, 877; m/z (ESI): 178.12(100%, [M+H]⁺).

5,5′-Bis-piperidino-2,2′-methandiyl-di-phenol

N-(3-Hydroxyphenyl)piperidine (1.50 g, 8.52 mmol) was added to MeOH (20cm³). The mixture was cooled to 5° C. in ice before HCl (486 μl, 4.26mmol, 32%) was added. Formalin (327 μl, 4.26 mmol, 39%) was added to thereaction mixture. The reaction was stirred at 5° C. for 18 h, and thenat 30° C. for 18 h. The reaction mixture was poured into H₂O (30 cm³)and the resulting mixture neutralised by the addition of an aqueoussolution of NaHCO₃ (sat.). The mixture was extracted with DCM (3×30 cm³)and the combined extracts dried (Na₂SO₄). The solvent was removed underreduced pressure. Column chromatography (3:7 EtOAc/Hexane (Rf: 0.4)]gave the product as a purple/pink solid (886 mg, 57%).

δ_(H) (250 MHz, CDCl₃): 7.06 (2H, d, J=8 Hz, ArH), 6.44 (2H, d, J=8 Hz,ArH), 6.23 (2H, s, ArH), 3.72 (2H, s, CH₂), 2.96-2.83 (8H, m, 4CH₂),1.70-1.56 (8H, m, 4CH₂), 1.56-1.40 (4H, m, 2CH₂); δ_(c) (62.5 MHz,CDCl₃): 153.4, 151.7, 130.8, 119.9, 110.1, 105.4, 51.3, 30.2, 25.4,24.2; ν_(max) (KBr)/cm⁻¹: 3268, 2928, 2854, 2798, 1618, 1577, 1522,1497, 1447, 1383, 1253, 1177, 1115, 969; m/z (ESI): 367.24 (100%,[M+H]⁺).

3,6-Bis-(piperidino)xanthylium nitrate

H₂SO₄ (900 μl, 98%) was added to H₂O (100 μl) and cooled to roomtemperature. 5,5′-bis-piperidino-2,2′-methandiyl-di-phenol (350 mg,0.956 mmol) was added and the mixture heated to 140° C. under N₂ for 3h. The resulting solution was cooled to room temperature and H₂O (5 cm³)added. The mixture was neutralised by the addition of NaOH (40%) whilstmaintaining a reaction temperature of less than 20° C. HCl (700 μl, 32%)was added and the reaction stirred at room temperature for 30 min. underN₂. FeCl₃.6H₂O (516 mg, 1.91 mmol) in H₂O (3 cm³) was added and themixture heated to 80° C. for 2 h in air. The reaction was allowed tocool to room temperature overnight whereupon a green oil precipitated.The bulk pinkish solution was decanted and the remaining oil taken up infresh H₂O (8 cm³). HNO₃ (few drops, 70%) was added slowly until a greensolid precipitated. This was collected by filtration and dried undervacuum. Column chromatography (1:9 MeOH/DCM (R_(f) 0.2)] gave theproduct as a green solid (117 mg, 30%).

δ_(H) (250 MHz, CD₃OD): 8.51 (1H, s, ArH), 7.77 (2H, d J=9 Hz, ArH),7.30 (2H, d, J=9 Hz, ArH), 7.07 (2H, s, ArH), 3.86-3.72 (8H, m, 4CH₂),1.90-1.66 (12H, m, 6CH₂); δ_(c) (100 MHz, CD₃OD): 158.5, 157.1, 144.9,133.1, 114.5, 96.6, 46.9, 25.7, 23.9; ν_(max) (KBr)/cm⁻¹: 2928, 1653,1577, 1560, 1490, 1384, 1244, 1169, 1017; m/z (ESI): 347.21 (100%,[M−NO₃]⁺).

Synthesis 22 3,6-Bis-pyrrolidino-xanthylium nitrate

N-(3-Hydroxyphenyl)pyrrolidine

Pd(OAc)₂ (129 mg, 0.578 mmol) was added to pyrrolidine (2.46 g, 34.68mmol) and 3-bromophenol (5.00 g, 28.90 mmol) under N₂.2,8,9-triisobutyl-2,5,8,9-tetraaza-1-phosphabicyclo[3,3,3]undecane (397mg, 1.16 mmol), LiHMDS (66.50 cm³, 1 M in THF) and dry toluene (110 cm³)were added sequentially. The mixture was heated to 80° C. for 18 h,before being cooled to room temperature. H₂O (50 cm³) was added and thelayers separated. The aqueous layer was extracted with toluene (3×40cm³). The combined organics were dried (Na₂SO₄) and the solvent removedunder reduced pressure. Column chromatography [3:7 EtOAc/Hexane (R_(f)0.5)] gave the product as an off-white solid (1.92 g, 51%).

δ_(H) (250 MHz, CDCl₃): 7.10-7.04 (1H, m, ArH), 6.18-6.11 (2H, m, 2ArH),6.05 (1H, s, ArH), 4.70 (1H, bs, OH), 3.30-3.20 (4H, m, 2CH₂), 2.01-1.96(4H, m, 2CH₂); δ_(c) (62.5 MHz, CDCl₃): 156.5, 149.5, 130.1, 104.8,102.5, 98.7, 47.7, 25.5; ν_(max) (KBr)/cm⁻¹: 3315, 2979, 2891, 2852,1618, 1578, 1518, 1491, 1459, 1217, 1202, 1170, 817; m/z (ESI): 164.11(100%, [M+H]⁺).

5,5′-Bis-pyrrolidino-2,2′-methandiyl-di-phenol

N-(3-Hydroxyphenyl)pyrrolidine (1.00 g, 6.13 mmol) was added to MeOH (15cm³). HCl (350 μl, 3.07 mmol, 32%) was then added. Formalin (236 μl,3.07 mmol, 39%) was added to the reaction mixture. The reaction wasstirred at room temperature overnight, and then at 30° C. for 24 h. Thereaction mixture was poured into H₂O (30 cm³) and the resulting mixtureneutralised by the addition of an aqueous solution of NaHCO₃ (sat.).

The mixture was extracted with DCM (3×30 cm³) and the combined extractsdried (Na₂SO₄). The solvent was removed under reduced pressure. Columnchromatography [3:7 EtOAc/Hexane (R_(f) 0.3)] gave the product as anoff-white solid (384 mg, 37%).

δ_(H) (250 MHz, CDCl₃): 7.01 (2H, d, J=8 Hz, ArH), 6.92 (2H, bs, OH),6.05 (2H, d, J=8 Hz, 2ArH), 5.93 (2H, s, ArH), 3.72 (2H, s, CH₂),3.13-3.00 (8H, m, 4CH₂), 1.96-1.85 (8H, m, 4CH₂); δ_(c) (62.5 MHz,CDCl₃): 153.2, 148.2, 130.8, 114.9, 105.3, 99.5, 47.7, 29.7, 25.4;ν_(max) (KBr)/cm⁻¹: 3389, 2967, 2834, 1624, 1560, 1515, 1483, 1431,1371, 1204, 1176, 1126; m/z (ESI): 339.21 (100%, [M+H]⁺).

3,6-Bis-(pyrrolidino)xanthylium nitrate

H₂SO₄ (500 μl, 98%) was added to H₂O (50 μl) and cooled to roomtemperature. 5,5′-bis-pyrollidino-2,2′-methandiyl-di-phenol (150 mg,0.419 mmol) was added and the mixture heated to 140° C. under N₂ for 3h. The resulting solution was cooled to room temperature and ice H₂O (1cm³) added. The mixture was neutralised by the addition of NaOH (40%)whilst maintaining a reaction temperature of less than 20° C. HCl (300μl, 32%) was added and the reaction stirred at room temperature for 30min. under N₂. FeCl₃.6H₂O (226 mg, 0.838 mmol) in H₂O (1 cm³) was addedand the mixture heated to 90° C. for 2 h in air. The reaction wasallowed to cool to room temperature overnight. The resulting solid wascollected by filtration and dried under vacuum. This material wasdissolved in H₂O (5 cm³) and HNO₃ (few drops, 70%) was added slowlyuntil a green solid precipitated. After 10 min the solid was collectedby filtration and dried under vacuum to give the product as a greensolid (121 mg, 71%).

δ_(H) (250 MHz, CD₃OD): 8.51 (1H, s, ArH), 7.74 (2H, d, J=9 Hz, ArH),7.00 (2H, d, J=9 Hz, 2ArH), 6.72 (2H, s, ArH), 3.69-3.52 (8H, m, 4CH₂),2.23-2.10 (8H, m, 4CH₂); δ_(c) (100 MHz, CDCl₃): 157.4, 155.0, 145.6,132.8, 114.7, 114.0, 96.2, 47.0, 24.7; ν_(max) (KBr)/cm⁻¹: 2961, 2865,1652, 1601, 1518, 1384, 1345, 1165, 820; m/z (ESI): 319.18 (100%,[M−NO₃]⁺).

Synthesis 23 3,6-Bis-morpholino xanthene dihydrochloride

3,6-Bis-morpholino xanthene dihydrochloride

H₂SO₄ (1 cm³, 98%) was added to water (100 μl) and the mixture cooled toroom temperature. 5,5′-Bis-morpholino-2,2′-methandiyl-di-phenol (300 mg,0.811 mmol) was added portion wise with stirring. The mixture was thenheated at 140° C. for 3 h under nitrogen. The resulting solution wascooled to room temperature before the addition of ice water (5 cm³). Themixture was neutralised by the slow addition of sodium hydroxide (40% inwater) keeping the temperature below 20° C. The resulting pinkprecipitate was collected by filtration, washed with water (2×3 cm³).The intermediate was added to a solution of methanol (5 cm³) and HCl(600 μl, 32%) and stirred for 30 min until homogeneous. The solvent wasremoved under reduced pressure and the solid dried under vacuumovernight to give the product as a purple solid (276 mg, 80%).

δ_(H) (250 MHz, DMSO-d₆): 7.24 (2H, d, J=8 Hz, 2ArH), 7.10-7.00 (2H, m,2ArH), 7.05 (2H, s, 2ArH), 3.94 (2H, s, CH₂), 3.92-3.81 (8H, m, 4CH₂),3.35-3.27 (8H, m, 4CH₂); ν_(max) (KBr)/cm⁻¹: 2916, 2866, 2637, 2581,1649, 1597, 1487, 1459, 1384, 1246, 1167, 1118, 1058; m/z (ESI): 353.19(100%, [M−HCl₂]⁺).

Synthesis 24 3,6-Bis-pyrrolidino xanthene dihydrochloride

3,6-Bis-pyrrolidino xanthene dihydrochloride

H₂SO₄ (900 μl, 98%) was added to water (100 μl) and the mixture cooledto room temperature. 5,5′-Bis-pyrrolidino-2,2′-methandiyl-di-phenol (100mg, 0.296 mmol) was added portion wise with stirring. The mixture wasthen heated at 140° C. for 3 h under nitrogen. The resulting solutionwas cooled to room temperature before the addition of ice water (5 cm³).The mixture was neutralised by the slow addition of sodium hydroxide(40%) keeping the temperature below 20° C. The resulting precipitate wascollected by filtration, washed with water (5 cm³). The intermediate wasadded to a solution of methanol (5 cm³) and HCl (400 μl, 32%) andstirred for 30 min until homogeneous. The solvent was removed underreduced pressure and the solid dried under vacuum overnight to give theproduct as a purple solid (84 mg, 72%).

δ_(H) (250 MHz, DMSO-d₆): 7.13 (2H, d, J=8 Hz, ArH), 6.70-6.58 (6H, m,6ArH), 3.87 (2H, s, CH₂), 3.40-3.29 (4H, m, 4CH₂), 2.10-1.94 (4H, m,4CH₂); ν_(max) (KBr)/cm⁻¹: 2984, 2658, 1604, 1508, 1492, 1384, 1345,1221, 1164, 1117, 1059, 1000; m/z (ESI): 321.20 (100%, [M−HCl₂]⁺).

Synthesis 25 3,6-Bis-piperidino xanthene dihydrochloride

3,6-Bis-piperidino xanthene dihydrochloride

H₂SO₄ (900 μl, 98%) was added to water (100 μl) and the mixture cooledto room temperature. 5,5′-Bis-piperidino-2,2′-methandiyl-di-phenol (350mg, 0.956 mmol) was added portion wise with stirring. The mixture wasthen heated at 140° C. for 3 h under nitrogen. The resulting solutionwas cooled to room temperature before the addition of ice water (5 cm³).The mixture was neutralised by the slow addition of sodium hydroxide(40%) keeping the temperature below 20° C. The resulting pinkprecipitate was collected by filtration, washed with water (2×5 cm³).The intermediate was added to a solution of methanol (5 cm³) and HCl(600 μl, 32%) and stirred for 30 min until homogeneous. The solvent wasremoved under reduced pressure and the solid dried under vacuumovernight to give the product as a purple solid (298 mg, 74%).

δ_(H) (250 MHz, DMSO-d₆): 7.73 (2H, s, ArH), 7.65 (2H, d, J=8 Hz, ArH),6.47 (2H, d, J=8 Hz, ArH), 4.12 (2H, s, CH₂), 3.64-3.47 (8H, m, 4CH₂),2.20-1.89 (8H, m, 4CH₂), 1.77-1.57 (4H, m, 2CH₂); ν_(max) (KBr)/cm⁻¹:2951, 2522, 1613, 1504, 1479, 1447, 1412, 1300, 1272, 1225, 1198, 1154,1119; m/z (ESI): 349.23 (100%, [M−HCl₂]⁺).

Synthesis 26 2,6,10-tris-diethylamino-4,8,12-trioxatrianguleumhexafluorophosphate

Laursen, B. W., Krebs, F. C., Nielsen, M. F., Bechgaard, K.,Christensen, J. B., Harrit, N., Journal of the American ChemicalSociety, 120, 1998, 12255.

Tris-(2,4,6-trimethoxyphenyl)carbenium tetrafluoroborate

PhLi (20 cm³, 35.71 mmol, 1.8 M dibutyl ether) was added totrimethoxybenzene (5.00 g, 29.76 mmol) in dry benzene (20 cm³) under N₂.The reaction was stirred at room temperature for 5 days. Diethylcarbonate (1.17 g, 9.22 mmol) in benzene (30 cm³) was added and thereaction heated to reflux for 3 days, before being cooled to roomtemperature. The reaction mixture was poured into NaOH (60 cm³, 1 M).the mixture was extracted with diethyl ether (3×40 cm³) and the combinedextracts dried (MgSO₄). HBF₄ (2.3 cm³, 48%) was added to the solutionand the resulting precipitate collected by filtration and dried undervacuum. The solid was dissolved in CH₃CN (30 cm³) and H₂O was addeduntil precipitation of the product occurred. The bulk solution wasdecanted and the residue dried under vacuum. Column chromatography [1:9MeOH/DCM (R_(f) 0.2)] gave the product as a green solid (1.68 g, 28%).

δ_(H) (250 MHz, CDCl₃): 6.04 (6H, s, 6ArH), 3.97 (9H, s, 3OCH₃), 3.57(18H, s, 6OCH₃); ν_(max) (KBr)/cm⁻¹: 2941, 1594, 1560, 1474, 1420, 1260,1229, 1166, 1118, 1084, 1060, 1022; m/z (ESI): 513.21 (100%, [M−HBF₄]⁺).

Tris(4-diethylamino-2,6-dimethoxyphenyl) carbenium hexafluorophosphate

Tris-(2,4,6-trimethoxyphenyl)carbenium tetrafluoroborate (270 mg, 0.450mmol) was dissolved in NMP (3 cm³). Diethylamine (7.56 g, 0.103 mol) wasadded and the reaction stirred at room temperature for 9 days. Themixture was then poured into an aqueous solution of KPF₆ (20 cm³, 0.2M). The mixture was then stirred at room temperature for 1 h, collectedby filtration and dried under vacuum to give the product as a green/bluesolid (295 mg, 84%)

δ_(H) (250 MHz, CDCl₃): 5.71 (6H, s, 6ArH), 3.60-3.21 (30H, m, 60CH₃ and6CH₂), 1.24 (18H, t, J=7 Hz, 6CH₃); δ_(c) (100 MHz, CDCl₃): 163.3,153.9, 114.9, 88.4, 56.0, 45.2, 13.0 (1 carbon missing); ν_(max)(KBr)/cm⁻¹: 2974, 1595, 1507, 1458, 1386, 1340, 1269, 1124, 1076, 843;m/z (ESI): 636.40 (100%, [M−HPF₆]⁺).

2,6,10-Tris-diethylamino-4,8,12-trioxatrianguleum hexafluorophosphate

Tris(4-diethylamino-2,6-dimethoxyphenyl) carbenium hexafluorophosphate(250 mg, 0.32 mmol) and LiI (428 mg, 3.20 mmol) were added to NMP (25cm³). The mixture was heated to 170° C. for 4 h under N₂. The reactionwas allowed to cool to room temperature overnight before being pouredinto an aqueous solution of KPF₆ (125 cm³, 0.2 M). The resulting orangeprecipitate was collected by filtration, and then dissolved in DCM (100cm³). The solution was washed with an aqueous solution of KPF₆ (2×30cm³, 0.2 M), dried (Na₂SO₄) and the solvent removed. Columnchromatography [1:2 EtOAc/DCM (R_(f) 0.35)] gave the product as anorange solid (96 mg, 47%).

δ_(H) (250 MHz, CDCl₃): 6.45 (6H, s, 6ArH), 3.53 (12H, q, J=7 Hz, 6CH₂),1.24 (18H, t, J=7 Hz, 6CH₃); δ_(c) (100 MHz, CDCl₃): 155.8, 150.3, 94.3,94.2, 46.0, 12.3; ν_(max) (KBr)/cm⁻¹: 2977, 1647, 1605, 1509, 1446,1349, 1281, 1139, 843; m/z (ESI): 498.27 (100%, [M−HPF₆]⁺).

Synthesis 27 3-Diethylamino-7-dimethylaminophenazinium chloride

3-Diethylamino-7-dimethylaminophenazinium chloride

-   Adapted from D. F. Gloster, L. Cincotta, J. W. Foley, J.    Heterocyclic Chem., 36, 1999, 25.

N,N-diethyl-1,4-phenylenediamine (1.00 g, 6.17 mmol) was added slowly todilute HCl (700 μl, 32%) in H₂O (100 cm³). The mixture was stirred untilit was homogeneous. N-[3-(dimethylamino)phenyl]methanesulphonamide (1.32g, 6.17 mmol) in methanol (60 cm³) was added, followed by a saturatedaqueous solution of potassium dichromate (2 cm³). The mixture refluxedfor 15 min. The mixture was cooled and diluted with water (200 cm³),acidified with hydrochloric acid (1M) and then extracted with chloroform(6×30 cm³). The combined extracts were dried over sodium sulphate,filtered and the solvent removed under reduced pressure. Columnchromatography (1:9 methanol/dichloromethane) gave the target materialas a green solid (451 mg, 22%).

δ_(H) (250 MHz, CDCl₃): 7.85 (2H, d, J=10 Hz, 2ArH), 7.30-7.25 (2H, m,2ArH), 6.97 (2H, s, 2ArH), 3.51 (4H, q, J=7 Hz, 2CH₂), 3.13 (6H, s,2CH₃), 1.26 (6H, J=7 Hz, 2CH₃);

m/z (ESI): 295 (26%, [M−Cl]⁺), 324 (100%).

Synthesis 28 3-Diethylamino-7-dimethylaminooxazinium perchlorate

3-Diethylamino-7-dimethylaminooxazinium perchlorate

-   Adapted from a procedure by: A. Kanitz, H, Hartmann, Eur, J, Org,    Chem., 1999, 923.

3-Diethylaminophenol (1.10 g, 6.67 mmol), N,N-dimethyl-4-nitrosoaniline(1.00 g, 6.67 mmol) and perchloric acid (1 cm³) were heated together inethanol (30 cm³) for 5 min. The reaction was allowed to cool to roomtemperature. The resulting solid was collected by filtration and driedunder vacuum overnight. Column chromatography (1:9methanol/dichloromethane) gave the product as a green solid (184 mg,7%).

δ_(H) (250 MHz, CDCl₃): 7.76-7.71 (2H, m, 2ArH), 7.19-7.14 (2H, m,2ArH), 6.98-6.95 (2H, m, 2ArH), 3.75 (4H, q, J=7 Hz, 2CH₂), 3.43 (6H, s,2CH₃), 1.39 (6H, J=7 Hz, 2CH₃); m/z (ESI): 296 (100%, [M−Cl]).

Example 2 Activity and Therapeutic Index In Vitro Assay for EstablishingB50

This is described in detail in WO 96/30766. Briefly, a fragment of taucorresponding to the core repeat domain, which has been adsorbed to asolid phase substrate, is able to capture soluble full-length tau andbind tau with high affinity. This association confers stability againstproteolytic digestion of the aggregated tau molecules. The process isself-propagating, and can be blocked selectively by prototypepharmaceutical agents.

More specifically, truncated tau (residues 297-390; dGA) diluted incarbonate buffer (pH 9.6) was bound to the assay plate, and full-lengthtau (T40) was added in the aqueous phase. The aqueous phase bindingbuffer contained 0.05% Tween-20 and 1% gelatine in phosphate-bufferedsaline (pH7.4). Bound tau was detected using mAb 499 that recognises anN-terminal epitope within the aqueous phase full-length tau but thatfails to recognise the solid phase-bound truncated tau fragment.

The concentration of compound required to inhibit the tau-tau binding by50% is referred to as the B50 value.

Cell-Based Assay for Establishing EC50

The process is described in more detail in WO 02/055720. In essence,fibroblast cells (3T6) express full-length tau (“T40”) under control ofan inducible promotor, and low constitutive levels of the PHF-core taufragment (12 kD fragment). When T40 expression is induced, it undergoesaggregation-dependent truncation within the cell, N-terminally at ˜αα295 and C-terminally at ˜αα 390, thereby producing higher levels of the12 kD PHF-core domain fragment. Production of the 12 kD fragment can beblocked in a dose-dependent manner by tau-aggregation inhibitors. Indeedthe quantitation of inhibitory activity of compounds with respect toproteolytic generation of the 12 kD fragment within cells can bedescribed entirely in terms of the same parameters which describeinhibition of tau-tau binding in vitro. That is, the extent ofproteolytic generation of the 12 kD fragment within cells is determinedentirely by the extent to tau-tau binding through the repeat domain. Theavailability of the relevant proteases within the cell is non-limiting.

Results are expressed as the concentration at which there is a 50%inhibition of generation of the 12 kD fragment. This is referred to asthe EC50 value.

Toxicity in Cells LD50 and Therapeutic Index (RxI)

Toxicity of the compounds described herein was assessed in the cellbased assay used to assess EC50. Toxicity was measured by cell numbersafter 24 hrs exposure to the compound using a lactate dehydrogenaseassay kit TOX-7 (Sigma Biosciences) according to the manufacturer'sinstructions after lysis of remaining cells. Alternatively a kit fromPromega UK (CytoTox 96) was used, again according to the manufacturer'sinstructions.

The therapeutic index (RxI) was calculated as follows: RxI=LD50/EC50.

TABLE 2 Activity and Therapeutic Index of Compounds A to O Compound B50(μM) EC50 (μM) LD50 (μM) RxI MTC  218 ± 20.1 (6)  0.59 ± 0.04 (69) 65.0± 5.0 (38) 110 DMMTC 3.4 ± 0.2 (2)  0.04 ± 0.004 (22) 2.7 ± 1.2 (6) 67DMAXC 38.5 ± 6.9 (3)   0.2 ± 0.11 (2) 39.2 ± 10.5 (5) 196 A 33.8 ± 5.2(3)  0.0061 ± 0.0024 (9)   19 ± 2.7 (22) 3115 B 254.1 ± 26.4 (3)  0.0081± 0.0035 (9) 30.8 ± 4.6 (4)  3802 C 461 ± 130 (3) 0.47 5.99 ± 2.6 (4) 13 D 49.4 ± 7.6 (5)  0.017 ± 0.01 (4)    30 ± 3.4 (10) 1764 E* 312.1 ±28.4 (7)  0.014 ± 0.002 (7) 15.8 ± 2.8 (16) 1131 389.6 ± 322.0 (2) 0.048 ± 0.008 (17) 19.37 ± 2.3 (7)  404 F 260.1 ± 57.1 (3)  0.042 ±0.030 (5) 24.6 ± 6.3 (5)  586 G 89.4 ± 15.7 (3) 0.079 ± 0.024 (6) 35.8 ±5.5 (6)  453 H NE 0.054 ± 0.01 (10) 113 ± 18 (11) 2093 I•HNO₃ NE 0.032 ±0.007 (6) 20.4 ± 3.5 (8)  638 J NE 0.011 ± 0.006 (5) 17 ± 3 (10) 1545 KNE 0.23 ± 0.13 (3) 21.2 ± 12 (3)   91 L 21.7 ± 2.7 (3)  0.30  22 ± 8.6(3) 73 M 110.4 ± 6.2 (3)  0.44 NT NT N 93.1 ± 17 (3)   NT  136 ± 19.3(4) NT O 190.2 ± 33.2 (3)  3.9 ± 3.5 (3) 115 ± 17 (9)  29 AB 413.5 1.72± 1.0 (4)  78 ± 54 (6) 45 AC 129.4 ± 11.9 (3)  1.43 ± 0.14 (4) 14.5 ±8.4 (8)  34 AD 126.4 ± 3.0 (3)  0.35 ± 0.10 (5) 19 ± 9 (5)  54 AE 324.5± 87.1 (3)  0.051 ± 0.012 (5) 21 ± 8 (7)  412 AF 186.7 ± 28.3 (4)   22 ±4.2 (5) 144 ± 67 (10) 7 AG 257.1 ± 50.3 (5)  1.12 ± 0.75 (5) 13.8 ± 6.2(8)  12 AH 129.4 ± 15.5 (3)   0.26 ± 0.073 (9) 121 ± 52 (12) 465 AI NE16 ± 11 (3)  280 ± 121 (10) 17 AJ NE 0.37 ± 0.1 (6)  125 ± 57 (10) 334AK 284.1 ± 101.2 (5) 0.64 ± 0.27 (5) 44 ± 26 (8) 69 AL 8.5 ± 0.9 (3)0.13 ± 0.07 (4) 8 ± 4 (6) 62 AM 634.1  1.1 ± 0.24 (5) 93 ± 19 (6) 85 ANNE 0.54 ± 0.08 (4) 167 ± 29 (6)  309 NE = no effect when tested to 500μM. NT = not tested B50, EC50, LD50 values are expressed as mean values(in μM) ± SE, with number of replications in parentheses. RxI =EC50/LD50. *results from two different synthetic batches of compound E

REFERENCES

The following references are hereby incorporated by reference in theirentirety:

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The invention claimed is:
 1. A method of treatment of a tauopathycondition or a disease of tau protein aggregation in a patient in needthereof comprising administering to the patient a compound of formula(I):

wherein: X⁻ is a counter ion; —R⁵ is independently —H, or saturatedC₁₋₆alkyl, which is unsubstituted or substituted with one or moresubstituents —R^(5A), or phenyl, which is unsubstituted or substitutedwith one or more substituents —R^(5A); each —R^(5A) is independentlyselected from —F, —Cl, —Br, —I, —OH, —OR⁶, —SH, —SR⁶, —CN, —NO₂, —NH₂,—NHR⁶, —NR⁶ ₂, —NHC(═O)R⁶, —NR⁶C(═O)R⁶, —C(═O)OR⁶, —OC(═O)R⁶, —C(═O)NH₂,—C(═O)NHR⁶, and —C(═O)NR⁶ ₂, —C(═O)R⁶, —C(═O)OH, —S(═O)R⁶, —S(═O)₂R⁶,and —S(═O)₂OH; each —R⁶ is independently saturated aliphatic C₁₋₄alkyl,phenyl, or benzyl; —R^(13a), —R^(13b), —R^(14a), —R^(14b), —R^(15a),—R^(15b), —R^(16a), and —R^(16b) are each independently selected from Hand saturated aliphatic C₁₋₄ alkyl.
 2. A method according to claim 1,wherein X⁻ is selected from the group consisting of: NO₃ ⁻, ClO₄ ⁻, F⁻,Cl⁻, Br⁻, I⁻, ZnCl₃ ⁻, FeCl₄ ⁻ and PF₆ ⁻.
 3. A method according to claim1, wherein —R⁵ is independently —H, or saturated aliphatic C₁₋₆alkyl,which is unsubstituted or substituted with one or more substituents—R^(5A).
 4. A method according to claim 1, wherein —R⁵ is saturatedaliphatic C₁₋₄alkyl, which is unsubstituted or substituted with one ormore substituents —R^(5A).
 5. A method according to claim 4, whereineach —R^(5A) is independently selected from —F, —Cl, —Br, or —I.
 6. Amethod according to claim 4, wherein —R⁵ is —CF₃.
 7. A method accordingto claim 1, wherein —R⁵ is phenyl, which is substituted with one or moresubstituents —R^(5A).
 8. A method according to claim 7, wherein each—R^(5A) is independently selected from NH₂ and NO₂.
 9. A methodaccording to claim 4, wherein —R⁵ is -Et.
 10. A method according toclaim 1, wherein the compound is a compound of formula (Ic):

wherein X and R⁵ are as defined for the compounds of formula (I).
 11. Amethod according to claim 1, wherein the compound is selected from thegroup consisting of: Com- pound Structure and Name A

B

C

D

AE


12. A method according to claim 1, wherein the compound is provided inthe form of a dosage unit comprising the compound in an amount of from20 to 300 mg and a pharmaceutically acceptable carrier, diluent, orexcipient.
 13. A method according to claim 1, wherein the treatmentcomprises administration of the compound according to one of thefollowing dosage regimes: about 50 or about 75 mg, 3 or 4 times daily;or about 100 or about 125 mg, 2 times daily.
 14. A method according toclaim 1, wherein the treatment comprises oral administration of thecompound.
 15. A method according to claim 1, wherein the treatmentfurther comprises treatment with at least one of the following: acholinesterase inhibitor; Donepezil, Rivastigmine, or Galantamine; anNMDA receptor antagonist; Memantine; a muscarinic receptor agonist; aninhibitor of amyloid precursor protein processing to beta-amyloid.
 16. Amethod of reversing or inhibiting the aggregation of tau proteincomprising contacting the aggregate or protein with a compound asdefined in claim
 1. 17. A method of regulating the aggregation of a tauprotein in the brain of a mammal, which aggregation is associated with adisease of tau protein aggregation, comprising the step of administeringto said mammal a therapeutically effective amount of a compound asdefined in claim
 1. 18. A method of inhibiting production of proteinaggregates in the brain of a mammal, comprising the step ofadministering to said mammal a therapeutically effective amount of acompound as defined in claim
 1. 19. A method of treatment of a tauopathycondition in a patient comprising administering to said patient acompound as defined in claim
 1. 20. A method of treatment of a diseaseof tau protein aggregation in a patient comprising administering to saidpatient a compound as defined in claim
 1. 21. A method of treatment ofAlzheimer's disease (AD), Pick's disease, Progressive Supranuclear Palsy(PSP), fronto-temporal dementia (FTD), parkinsonism linked to chromosome17 (FTDP-17), disinhibition-dementia-parkinsonism-amyotrophy complex(DDPAC), pallido-ponto-nigral degeneration (PPND), Guam-ALS syndrome,pallido-nigro-luysian degeneration (PNLD), cortico-basal degeneration(CBD), Dementia with Argyrophilic grains (AgD), Dementia pugilistica(DP), Down's Syndrome (DS), Dementia with Lewy bodies (DLB) Subacutesclerosing panencephalitis (SSPE), MCI, Neumann Pick disease, typeC(NPC), Sanfilippo syndrome type B, mucopolysaccharidosis III B (MPS IIIB), myotonic dystrophies (DM), DM1 or DM2, or chronic traumaticencephalopathy (CTE) in a patient, comprising administering to saidpatient a compound as defined in claim
 1. 22. A method of treatment ofAlzheimer's disease (AD) in a patient, comprising administering to saidpatient a compound as defined in claim 1.